I’ve never owned a 35mm film camera with an underwater housing. Given that I have to concentrate on dry land to make sure I don’t chop peoples’ heads off in the photo, taking a camera underwater was going to be a pointless exercise for me.  Never mind the expense, preparation time, weight and hassle, I was only ever going to end up with partial, nearly shots of my intended subject.  Not for me the Nik V and the like or counting the precious shots on the film.  I have a set of childhood photos which are peppered with shots of the clothes I was wearing and miss my posed, smiling face. My dad set the family standard for photography! I have recognised my limitations and therefore I do not possess a matching underwater portfolio of partial shots with seals, nudibranchs or urchins, or in the worst case yet another bit of seaweed or rockface.

The rise of digital cameras has been a bonus for me both above and below the water.  As a parent I’m fine with letting my kids off to play with a camera, knowing that I won’t be paying Boots a small fortune to develop two photos of the wedding reception and 22 out of focus photos of the tablecloths, carpet and the back of my son’s eye (well it can be hard to get the camera the right way round!).  Digital cameras have solved this….take as many photos as you like and then use the handy delete button. I don’t miss the sympathetic and slightly patronising look from the man behind the counter as he hands over a packet of 6x4 prints where 75% of them are stickered to advise me to focus carefully, avoid putting fingers over the flash etc. Digital cameras; remove memory card, review shots, delete rubbish, save to file with a vaguely memorable name. Job done!

So now I do have an underwater camera…. I do concentrate, I do try and line everything up, but if I fail then I don’t need to pay the photo developers for the privilege of finding out. To be honest, I know I will never publish a book of my underwater photos and I am in awe of those who manage to get some amazing shots. I lack time, patience and skill. My father taught me all he knows!

My latest toy is an HD video camera in a housing. The little LCD screen on the back helps me aim it in generally the right direction and so far things are looking promising. I’ve had some great recreational dives with year with the camera, carried out some marine surveys and been documenting wreck sites. I have hit a slight snag as now I need to learn to edit my video.  I see this as similar to deleting the frames where I let go of the camera to check my handset and gauges, but forgot to turn the camera off, or even where I just let go of the camera and it floated up on its lanyard for a bit.

Purists will tell me to weight the housing, but my policy of letting my camera float saved everything earlier this year.  A nice spell of calm weather meant we dived all four wrecks on Abu Nahas in the Red Sea. On dive 2 my camera wasn’t there when I reached for it, and I assumed I’d left it in the RIB, but when I got back to the surface there was no camera waiting.  The crew were great, we searched for 20 minutes over the site.  Other divers started to surface and we abandoned my camera to pick them up.  A few minutes more searching and we started back to the boat, with me lamenting that I hadn’t downloaded the photos from my sister’s hen party from the card. Nearly a half a mile from the wreck we found my floaty housing bobbing along.  It had been lost for nearly 2 hours! So in my book, floaty is good.
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That’s not always the case though. I guided a party of visiting divers on the wreck of the SS Liverpool this summer. I dropped down the shot marvelling at the 20+ metres of vis and turned to find a totally panicked wide-eyed diver behind me. His floating handle on his little video camera had pulled the lanyard off his wrist on his journey down the shot. He caught it before it floated away, but the lanyard became knotted around his regulator hose.  On a 40m wreck dive, with a hint of narcosis this wasn’t looking like a great situation. In his case, a floaty housing was definitely bad! I stopped filming and disentangled him, put his camera back on his wrist and the rest of the dive continued without incident. I hope he’s put weights on his housing now!
 

Most divers aim to be self sufficient, carrying spares, able to effect running repairs and with a wide skill set that covers boat handling, dive planning and responses to emergencies.  But sometimes there are situations in which outside help is required and we look to organisations such as the coastguard or the RNLI to assist. A quick peruse through the latest BSAC Incident Report reveals how often we rely on these services, and yet in our normal diving activities we probably don’t even consider them beyond noting the phone numbers on the dive management plan.

I’ve recently spent a thoroughly entertaining and informative evening with one of our local lifeboat stations. Following an incident last year, it had become obvious to both myself and the Lifeboat Operations Manager that there were some developing gaps in the understanding of their crew regarding dive kit and dive practises. So we set out to remedy that and the first step was to take some kit in for a bit of a theory session. Some of the older crew members had dived in the past, but many of the newer crew hadn’t. Presumably these were the guys we’d overheard saying “There’s no way you’d get me diving, it kills people.” It wasn’t hard to spot the need for some reciprocal training!

Accompanied by one of my assistant instructors, we lugged scuba kit and a rebreather up the staircase into the Lifeboat Station training room. Next time I will definitely remember to take my trim weights out of my Evolution! First things first though; a cup of tea and a chance to say hello. I haven’t met a lifeboat crew yet who didn’t revolve around tea. Once we got started, we talked through the kit, focusing on how understanding removing the equipment safely would aid the recovery of a casualty onto their Atlantic 85 RIB. Even the crew who had already had some diving experience got stuck into trying the different clips and releases. The big learning curve came when we looked at the rebreather. The growing number of rebreather divers throughout the UK means rescue services are now much more likely to encounter a rebreather unit on a casualty. We had a great discussion on some of the different risks that rebreathers can expose divers to, not just the 3Hs (hyperoxia, hypoxia and hypercapnia ) but also non freezing cold injuries from extended dive times. There were some lively discussions and great questions.

But our visit wasn’t just about the kit, we also took copies of the Incident report, and we talked about the numbers of incidents a year, and even read through some of the reports.  We took the British Diving Safety Group Accident flowchart with us and explained what actions divers would be trained to take. The big surprise came when I challenged their perception about diving as a dangerous sport, showing how few fatal incidents actually occur each year. I’ve given them the link to the BSAC website to access the other Incident reports too, and I know that as I left they were already searching the website.

There is more to come of course. The Operations Manager and I have set up a couple of joint training sessions to give the crew some practical experience. All my Dive Leader trainees are going to take part, and I’ll go through the Practical Rescue Management theory with them in advance. We are planning to set various scenarios that allow both groups to develop their skills and understanding. What a superb learning opportunity and a great way to build a relationship with the crew that we hope we will never actually need to call out.  In fact, I’d love to be in the position of only calling them so see if they want a pint after we’ve finished (although I guarantee they will be trying to make more tea!).
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During the winter months when the weather is reducing the number of dive opportunities, this seems like a good way to arrange some training, with both our instructors and Dive Leader trainees benefitting. Maybe DOs and TOs should be actively seeking to partner an RNLI station and foster just this sort of relationship? I wouldn’t go so far as to suggest ‘twinning’ as I suspect that any dive club advertising that it is ‘twinned’ with a lifeboat station would suffer a drop in recruitment! But I am convinced that a closer relationship between divers and the rescue service personnel can only be a good thing. I know these links exist at higher levels, isn’t it time the ground level guys were involved too? Dive safe!

​I’m something of a diving evangelist; I’m happy to help new divers, old divers and lapsed divers, from whatever brand of training they subscribed to.  There are a myriad of reasons why divers fall out of the habit, though I suspect that families and finance are the big ones.  Young families are an enormous drain on time and resources and I’m sure I’m not the only diving parent just ticking the time away until junior can undertake diver training and we can set out on a diving adventure together.  My diving will be massively improved with my guilty conscience at leaving my offspring finally expunged.
But when is it time to hang up your fins?  At what point does diving just not make sense anymore even if you love the sport and have spent years involved in it?  None of us like to admit we are growing older, less capable and more vulnerable….but time keeps moving on and our bodies are programmed to decay.  Accumulated injuries and life’s wear and tear start to take their toll. 
I laughingly joke after a full day of diving and training that this is a young man’s game – it’s not a joke but a heartfelt cry of anguish.  I’m learning to pace myself, something I would never have thought about in my 20’s.  Nitrox is my very best friend even for shallow training sessions.  It takes the edge off the sub-clinical DCI that we all experience, leaving me less tired and capable of keeping going.  But I know that in reality I am just compensating for the effects of getting older.
But at what point does is the compensation not enough?  I’ve had the honour of trying to assist a once excellent and accomplished diver back into the water after a break of over 15 years.  It has been a challenge for both me and the diver.  The equipment and skills have changed and we have worked in the safety of the pool.  But the real changes are the personal ones, physical strength and mental processing.  I’ve changed my approach entirely from one of assisting a fellow instructor to one of just trying to keep this diver and any potential buddies safe. 
I think one of the key factors with someone I have trained from scratch is that they are aware of the dangers and aware of their own limitations.  By contrast, taking someone who, in their day, was one of the foremost divers and instructors in their club is a scary proposition.  Without trying to be harsh, I find myself as Diving Officer mentally registering a huge number of limitations including possible buddies, depths and conditions.  This is taking all my people skills and has reawakened branch politics and disagreement from years before I even started diving!
So what have I learned?  In future I will try not to be over-awed by any diver’s past glories, but instead rely on my own observations regarding ability.  Returning divers rarely take up the offer to attend Ocean or Sports diver lectures, but refreshing theory knowledge is essential especially if the subject matter has moved on.  Mainstream diving has changed.  My offer of Nitrox was met with incredulity. The Devil’s gas?  And you give it to Ocean Divers?! But my motives were entirely about trying to keep my elderly friend safe.  .
And the really big lesson is trying to judge when to give up on diving altogether.  Will I notice when the time has come for me?  Will I be able to look at my physical state and work out that my diving days are behind me? Or will I be the one looking for a sympathetic Diving Officer willing to work out how to achieve my one last dive?  Do I set the limits now?  I will give up diving when I can no longer carry my own cylinder?  (But then we have disabled divers now for whom we carry kit around.)  I will give up diving when the instructors are 40 years younger than me?  I will give up diving when it seems like too much hard work?
The incident reports in the last few years have highlighted a possible increased risk to elderly divers.  Maybe it’s time to bring back a diving medical for specific sections of the diving community, perhaps the over 60’s?  And maybe that defines the end point of my diving too.  When I can no longer pass the rigorous HSE diving medical I will give up diving altogether.  Instead of waiting until I start to endanger myself and others, if I can’t make the medical I need for professional instructing, it will be time to hang up the fins and watch my children continue in the sport I love.  For now I will make the most of the time that our diving overlaps.

Somewhere way back in your training, you were probably introduced to the Incident Pit. It’s a fairly dramatic diagram with the words “fatal” and “death” appearing at the bottom. The concept was meant to inspire you to deal with problems early, keep control and stay safe, with the tag line “Don’t fall in.” This always seemed to be a slightly strange thing to say to divers, who are destined to fall in (to a body of water) quite deliberately. Other than encouraging you to run through your own personal risk assessment for a dive, that’s about all the standard training material has to say about pre-dive thinking.
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In many sports the technique of visualisation is used to help elite athletes achieve their potential, and there’s good evidence that it works at lower levels too. Visualisation is the process of creating a mental image of what you want to happen or feel in reality. An athlete could use this technique to picture crossing the finishing line first. For a diver there is clear potential to visualise a relaxed, in control dive and achieve a state of calm and well-being before a dive. In fact, most people naturally tend to think through and rehearse what’s about to happen to them. So quite possibly you have started to think this way already.

Sometimes these preparatory thoughts can be plagued with recurring images of past mistakes or near misses, and that’s not conducive to ensuring the success of the upcoming dive. It can be more helpful to actively direct your pre-dive thoughts and control those images in your head. And the visualisation probably needs to be more than just a visual experience. To really be successful, you would need to focus on all the senses; the rush of cold water, the smell of the sea, the feeling of pressure on your legs as you enter the water, the sound of your bubbles.

When you visualise the successful dive, you are stimulating the same regions of your brain as you do when you physically perform the same action. So, thinking the dive through, with all it’s stages, is a way of conditioning your brain for a successful outcome. Perhaps the visualisation starts before the dive, right back to the preparing your equipment. And the beauty of this preparation is that you could be doing it anywhere. Picture being on the bus thinking about packing your kit for the weekend.

What if we extend this to thinking through the different situations that may arise underwater? Rather than the scary prospect of the Incident Pit, why not challenge divers to visualise their response to common problems? What would they do if their torch fails on a night dive? It’s too easy to just say “I’d get my back up torch out”. In order to visualise it you would have to work through being able to open your BCD pocket (feel the zipper in your hand, hear the zip and feel as it bumps along the teeth), feel through the gloves for the piston clip, unclip the torch lanyard from the D ring, feel the lanyard in your hand etc. Which pocket? What else in in there to avoid dislodging? How will the torch feel in my hand? This is a far more powerful psychological technique than a glib “Get my back up” response.

For divers just starting out on their diving journey, visualisation can be an excellent way to deal with the nervous trainee. Try to remember the first time you put all your dive kit on. How tight did your neck seal feel? How restricted was your movement? These are things we all take for granted now. We have done it often enough that we barely register the sensation. I think there is a real value in talking through that first dive. This is not part of your SEEDS brief, this is so much more. Find a quiet space, sit down and step your way through the dive, start building the neuronal connections in a positive way and help boost performance.

It doesn’t matter how carefully you monitor your fluid intake before a dive, or how close to dive time you leave the last toilet visit, we have all got out from a dive ready to rugby tackle anyone standing between us and the toilet. It’s well known that going for a dive causes an increased need to urinate. There are some interesting physiological changes that come to play. Immersion and temperature changes cause a narrowing of the blood vessels in the extremities. This results in an increased volume of blood to the central organs which is interpreted by the body as fluid overload. This causes the production of antidiuretic hormone (ADH) to stop, signalling to your kidneys that they need to produce urine to lower the blood volume. So even if your last toilet visit was only minutes ago, you can quickly find yourself feeling the need to go again.
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It’s almost impossible to give an exact measurement for the volume of the human bladder as everyone’s ability to hold urine varies. Normal adult bladders hold between 300 and 400ml but can hold up to 600 or even 1000ml in some cases. The need to urinate is stimulated by the expansion of the bladder which triggers the Micturition reflex centre in the spinal cord. Most adults will feel the need to urinate when their bladder is only around a quarter to a third of its normal capacity. In normal circumstances, adults will feel the need to empty their bladder about every 3 hours, but as divers we know the effect that immersion plays.

There’s always a big debate in the wetsuit diving community about whether peeing in a wetsuit is acceptable or not. In a drysuit, the debate becomes somewhat redundant unless you have a P-valve fitted. But is there any danger to ‘holding it in’? When you first feel the need to pee, your bladder probably has quite a way to go before it’s completely full. As your bladder fills up the muscles around it will contract to keep urine from leaking out until you’re ready – just make sure you can get out of your suit fast enough!

The dangers of holding your pee are mostly cumulative, so the occasional episode probably isn’t harmful. However, if you are diving frequently and often find yourself ignoring the need to pee you run the risk of urinary tract infections, urinary retention (the muscles can’t relax even when you want to pee) or bladder atrophy (leading to incontinence). But for most people, you can hold your bladder full for a few hours without serious complications, even though its uncomfortable.

If you dive in a wetsuit, you can of course make the call as to whether you pee in your suit or not. The old saying is that 50% of divers pee in their wetsuits and the other 50% are liars. So whichever camp you fall into, just make sure you flush your suit through before you get out of the water and start to take it off, and please wash your suit thoroughly between dives.  If you’re a drysuit diver, there’s always the option of adult nappies to ensure that you can relieve yourself. If that seems a little retrograde, or as you march middle age a little too prophetic, then perhaps a P-valve is an option.

Not surprisingly there are hazards associated with P-valves too. Ignoring the issues with getting a stick-on condom or the female cup attached successfully, so that the urine does actually enter the tubing to leave suit, there are reported cases of urinary sepsis. The tubing used to connect the urine to the P-valve is the ideal breeding ground for Pseudomonas bacteria, and it only takes a small amount of backward flow to introduce those bacteria into the body. If you think rinsing your wetsuit is a bit of a faff, syringing antiseptic through P-valve tubing should give you some perspective.

We’ve had a rather enjoyable club trip away during the winter.  A chance to escape the grey, wet and cold and get a bit of sunshine. It helped that the trip was planned as part of an Advanced Diver exped, as that meant I didn’t actually have to do much to smooth the whole trip along. Our AD candidate had picked a BSAC centre to go diving with, assuming this would mean that our reasonable levels of experience (including First Class Divers and instructors) would be recognised and we would be treated accordingly. The dive plan was submitted by email and when we arrived the owner of the dive centre went to quite some lengths to tell us he was going to follow our plan exactly.

Day 1 wasn’t so bad, apart from a really strange conversation about compasses, and how if you look at your compass and it says 90 degrees then you are in fact swimming West. We tried to explore this assertion, after all it would mean rethinking the entire way we brief for dive sites, skipper boats and well, just generally everything. How could we have all got this far and been 180 degrees out? We asked if this was caused by having a compass with a sighting window, maybe looking at it from the top, but nope.  We were assured that 90 degrees was West. End of discussion, let’s go diving.  We took our own compass bearings on the shore (safe bearing was North). Our check out dive took a strange turn when instead of the 15 metre bimble we’d been briefed for we ended up at a 32 metre wreck. During the surface interval, we were assured that this dive had been in the plan, but even the AD candidate looked puzzled and it was her plan! Whilst on the surface we asked about the time for the second dive. It was a mandatory hour away, but who knows why it’s an hour. A couple of us tried to look at our plan functions to gauge when we’d have enough dive time for the next dive but we were stopped because “decompression is only a theory anyway”. We were doing an hour on the surface and then we’d be going back in.

By the next day, things took another turn for the bizarre. The first dive brief of the day explained that the dive 1 would be out from the harbour and turn right, and the second dive at the same site would be out and turn left. The first dive was pretty good, shoals of fish and a couple of angel sharks. We came back to the shore, had a bite to eat and swapped cylinders. Whilst we were standing in the sun to warm up a bit, someone asked about the topography for the second dive. At this point the story changed, we were told that there was nothing to the left apart from barren rocks, our dive guide couldn’t imagine why anyone would want to turn left, or who had suggested we should and we would be going right again. The second dive to exactly the same site was disappointing.  The tide had changed, the shoals of fish had moved on and we resorted to a little bit of wombling to clean up the reef.

By now we had established that we were becoming the victims of gaslighting. Gaslighting is a form of persistent manipulation and brainwashing that causes the victim to doubt her or himself, and ultimately lose her or his own sense of perception, identity, and self-worth. The term is derived from the 1938 stage play Gas Light, in which a husband tries to convince his wife that she’s insane by causing her to question herself and her reality, flickering the gas lights as he does. Despite having been around for over 75 years, the term has recently resurfaced with Trump’s presidency in the USA.
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We had the classic signs; blatant lies, denial of what had been previously agreed and attempts to manipulate and divide opinion the group. Once we’d identified that this sort of behaviour was in play, everyone’s guard was up. Fortunately, we’ve all know each other for a long time and dived together for many years. Each night our dinner and beer debrief covered very little about the dives and much more about the bizarre antics. The carefully written up dive plan that was the point of the trip had disappeared and was never mentioned again. Next time we’re all going to put our basic qualification and not mention any further diving experience. We think it will be easier all round. 

Before 1920, having tanned skin was associated with working outdoors and indicated that you carried out manual labour. The societal ideal was pale skin which showed that you were rich enough to stay indoors, although the pursuit of pale skin often involved powders containing lead and mercury, which weren’t exactly great choices from a health perspective.  The Western Europe attitudes started to change in the 1920s when Coco Chanel started to popularise the idea of a tanned skin, and this trend accelerated through the explosion in cheap air travel from the 1960s, so that having a tan showed you could afford to take the time off work and lounge around catching some sun’s rays.

The concept of desirable skin colour varies around the world. Whites try to tan, whilst across Asia the sale of skin lightening creams and lotions is at an all time high. Your natural skin tone is determined by genetics and that is directly correlated to how much UV radiation you are exposed to. The higher the level of UV radiation, the darker the tone of indigenous skin. As some populations of humans moved to more northern latitudes there was a shift in genetics. With less UV radiation causing damage, there was a positive selection of individuals with lighter skin, who could synthesise more vitamin D. As societies changed from hunting to agriculture, there was a need to maximise the vitamin D synthesis to make up for the loss from the diet. About 40,000 years ago the mutations for pale skin emerged in both the East Asian and Western European populations.

The most important pigment in the skin is called Melanin. Specialised cells call Melanocytes make the pigment and pack it into the Keratinoctyes that make up a layer in the skin.  Melanin is an important molecule as it controls the amount of UV radiation that can penetrate the skin. Some UV radiation is needed for vitamin D synthesis, but too much is harmful. UV light is divided into 3 different wavelengths of light, UV-A, UV-B and UV-C.  UV-C and some UV-B are absorbed by the ozone layer in the atmosphere, which is a very good thing as without this absorption UV levels would be dangerously high (and quite possibly life on earth wouldn’t exist!). Some UV-B is absorbed by the epidermis (the upper layer of the skin but UV-A can penetrate further into the skin and interacts with the cells in the dermis. UV-B causes an increase in melanin production and UV-A causes the melanin molecules to change and become darker.

However, tanning is not the only consequence of UV exposure. Although no-one knew it during the 1960s, too much exposure to sunlight is the cause of 90% of all skin cancers, eye damage, immune system suppression and all the signs of ageing associated skin damage. As this message started to become understood, the tide has turned against tanning salons, and anyone out in the sun was urged to wear a hat, cover up exposed skin and slap on the sun cream….and then we hit another snag. In March 2018, Hawaii announced that it was bringing in laws to ban sun creams containing oxybenzone, which is the most widely used UV absorbing molecule in all sun creams in use today.

Once upon a time, Para-amino benzoic acid (PABA) was widely used in suncreams.  Patented in the 1940s PABA was the first molecule to be used absorb UV-B in sun creams, but it fell out of favour as it stained clothes and caused allergic reactions. Then came Oxybenzone as the next generation molecule with the ability to absorb UV-A and UV-B. Oxybenzone isn’t just used in sun cream, but as a UV protection for a wide range of plastics too.  Hawaii have recognised a study that showed that tiny amounts (microgrammes per litre) of oxybenzone cause coral larvae to stop moving around and prevented them from developing a hard skeleton. To understand the concept of just how toxic this is, that’s lethal levels at half a teaspoon in an Olympic sized swimming pool.
It’s time for a switch away from the UV absorbing molecules like PABA (still in use as the derivative padimate O) and oxybenzone. Perhaps we need to return to the mineral reflective suncreams with their chalky finish. Have a look at the label on your suncream. There are several alternatives hitting the market now, although for some of them the claims can be hard to verify. Perhaps the safest option for us and the environment would be to take the lesson from Victorian society and just cover up? Stop putting any plastic solutions into the sea including the lotions you slather on.

​In the depths of winter, there are two major factors that reduce diving time, low pressure weather systems and snot. As the air becomes colder and drier, the cells lining the nasal cavity have to work quite hard to warm and moisten the air that we breathe in. The cells producing the mucus are called goblet cells (which is a reference to their shape, not an instruction for what to do with the mucus). The mucus itself is a mix of proteins which contribute to the protective role in a number of ways; enzymes that can attack bacterial cell walls, antibodies to bind to pathogens and lactoferrin to mop up any free iron.
But the real star of the snot show is Mucin, a group of large proteins with lots of sugar molecules bound to the central regions of the molecule. These sugars are important as they allow the Mucins to have gel-like properties with an amazing water holding capacity. Aggregations of Mucin molecules are secreted by the cells lining the airways (and digestive tract too) and the sugar coating helps them to resist digestion. Over 20 human Mucin genes have been identified and the proteins that they produce help bind pathogens together, and are one of the reasons why you will make more snot when combatting a nasal infection.
It’s not just humans and other mammals that can make Mucin, a similar group of proteins is found in the most humble gastropods. We are all familiar with snail trails. (I’m sure that was my Nan’s phrase for a small child with streams of nasal mucus running down their top lip!) Snails move using a combination of their muscular foot and a lubricating slime. Now here’s where it starts to get strange, mollusc slime is a non-Newtonian fluid. It doesn’t follow the normal rules that govern viscosity in fluids, but rather changes as stress is applied to it. This explains why the same mucus can be used to allow snails to move and to bind to a surface. As the wave of contraction from the muscular foot of the snail acts on the sticky slime, the slime changes to become a free-flowing liquid. When the pressure is removed, the slime becomes gel-like again, allowing snails to lodge in overhangs and defy gravity.
For marine snails, it’s slightly harder to see the need for a lubricant, but it turns out that the slime trail for some species has even more functions. It’s a big commitment for some species to make a slime trail, estimated at up to 60% of their total energy use. Periwinkles will sniff out and follow fresh trails made by other molluscs to reduce this energy requirement. Mucus trails bind microalgae from the water when they are fresh and so they can be an excellent food source. Yep, that’s right, eating the algae from someone else’s snot trail is a good thing for Periwinkles, but please don’t try this at home!
Limpets are grazing feeders who return to their ‘home-scar’ on the rock every time the tide goes out. For them, the mucus trail is their route to find the carefully etched out rock into which their shell can clamp down to protect them from predators, sealed with a mucus layer to prevent them drying out. Not so much “Follow the yellow brick road” as “Follow the limpet snot trail” to get home. With the right conditions, you can see limpet snot trails on rocks as the tide falls.
For some molluscs, their slime trail is also important for mating. Chemical signals indicate the sex of the snail, allowing prospective mates to find and copulate. Male periwinkles can track down a female by following chemical markers in the slime. But the females of one species of periwinkle (Littorina saxatilis) turns off this signal to avoid mating. L.saxatilis live in dense colonies and like other periwinkles will mate up to 20 times a day throughout the year. This seems like a strange strategy for any species to survive, the general rule being that males mate as often as possible, whereas females try to be selective about mates.
Why would female L.saxatilis try to avoid mating? Males mount onto their mate and crawl around to the lip of the shell. This means that the female is then bearing the load of adhering both parties to the rock, and remember that our slime is non-Newtonian, more stress makes it flow. Having a male periwinkle on your back will double the stress and can result in both parties being swept off the safety of the rockline. For females, mating will increase their chances of being predated upon. So the female L.saxatilis turns off the sex signal in her slime. Males will still follow the slime trails, but it’s a 50:50 chance that they could be trying to mate with another male at the end of the journey.
Since Ancient Greece snail slime has been used in cosmetics. It contains high levels of hyaluronan which is a major component of the proteins that support our cells. It is freely available as a cosmetic claimed to promote the formation of collagen and help to improve skin structure. More seriously, hyaluronan is gaining popularity as a biomaterial scaffold which is helping the next generation of bioengineers to promote the formation of blood vessels in tissue engineering. Something to ponder when you are relegated to shore cover as you are too snotty to dive… 

​Normally the ferries coming to the Isle of Man run at sensible times, but there is one particular scheduled service that leaves the port of Heysham at 02.15. In the winter, when the only other crossing is 14.15, I seem to find myself on the ‘overnight’ boat far more often than I would like. The boat doesn’t load until at least 01.30, so for a couple of hours I usually try to sleep in the carpark. Cold, rainy and situated next to the nuclear power station, it’s not exactly conducive to any restful sleep. Even if I do doze off I still have that dreadful anticipation of being woken by the port staff to drive onto the car deck.
I’ve learned now to book one of the cabins on the ferry. Head to the customer services desk, collect the key and find the cabin with the beds made up ready. If I’m quick I can kick my shoes off and be asleep before the safety announcement. The journey is just under 4 hours and the arrival in the Isle of Man is accompanied by an announcement and the lights in the cabin coming on. It doesn’t feel like I’ve actually slept at all. After a short drive home, I usually try for more sleep, but it’s not always easy during the day. I usually need a good night’s sleep to recover from my acute sleep deprivation.
As divers we often travel some distance by road, ferry or plane to get to our dive destinations. Travel arrangements can involve early check-ins and sleeping in unfamiliar places. There is considerable research into the effect of sleep deprivation and its effect on behaviour, particularly for in relation to driving. Sleep deprivation has the same hazardous effect as being drunk. Research has shown that being awake for 17-19 hours impairs performance to an extent that is comparable to having a blood alcohol level over the drink driving limit for the UK. As drink-driving has now become socially unacceptable, how many of us are aware that our driving could be as impaired by lack of sleep?
I think back to my days living in London, getting up at 4am to tow the club boat to the South coast, two waves of two dives and some food followed by the drive home. The boat would be stowed away by about 10pm, so the last few hours of towing a rib would have had me well into the fatigue zone.  The evidence suggests that performance decline sets in after 16 hours awake, add this to sub-clinical decompression related post-dive tiredness and I think I was in dangerous territory.
How many times though do our trip risk assessments include fatigue? I got up at 5am this morning to collect a group coming in from the ferry. During the summer there is an 03.00 crossing from Liverpool arriving in the Isle of Man at 05.45. If I think I felt tired as I arrived at the ferry terminal – you should have seen the divers we collected! Some of them had managed a little sleep in the airline style seats, but not much. We’ve brought them back to the accommodation and sent them all to bed. We expect to be diving this afternoon, and one of the risks I’m now assessing is how much sleep they haven’t had.
I can’t find any specific research into the impact of fatigue on diving, but I am happy to accept that driving is a reasonably good surrogate activity. Drowsy drivers experience difficulty remembering the last bit of road and slower reaction times. Impaired cognitive and motor performance aren’t good for divers either. We learn about the impairment due to narcosis (with that amazing slide that has several pints of beer on!), but being awake for long periods is going to cause those effects without even stepping in the water. Maybe there are hints about this in our training, we do advise to have a good interval between flying and diving, but there’s nothing explicit regarding sleep deprivation. If you aren’t convinced that this is a problem, perhaps you should know that it’s been estimated that sleep deprivation is implicated in 1 in 5 road accidents. Sleep deprived drivers are much more likely to get angry with other road users and deal poorly with stressful situations (like navigating unfamiliar roads).
Caffeine can help, but only in the short term and not with all the aspects. It can improve alertness and reduce reaction time, but fine motor control isn’t improved even with high doses. So, I could send all the divers to the local coffee shop and insist they top up their espresso quota, but I know that won’t last. Instead, I hope they have their heads down and are napping now. Me? I’m too wide awake and writing columns instead!

​Sellafield is located across the Irish Sea on the Cumbrian coast and is approximately 32 miles from the Isle of Man, on a clear day you can just about see it. The main activities at the plant include reprocessing of spent fuel from nuclear power reactors and storage of nuclear waste. There are no longer any nuclear power plants in operation at the Sellafield site. It was built in the late 1940s to manufacture plutonium for atomic bombs and Sellafield is one of the most radioactive places on earth. In its prime the plant was releasing eight million litres of contaminated waste into the sea every day. In 1957 the plant became the site of the worst nuclear accident in Great Britain's history, The Windscale Fire. This was a blaze that raged for three days, releasing radioactive gases into the air. The discharge of low level liquid wastes from the Sellafield site in the north west of England is the most significant source of artificial radioactivity in the Irish marine environment.
Now the site is mainly used for nuclear fuel reprocessing, and this and other activities gives rise to the discharge of low level radioactive materials in the form of liquids and gases into the environment. These discharges are regulated by the UK authorities and limits for releases are set by the Environment Agency of England and Wales (EA). Liquid radioactive waste is discharged from the plant into the Irish Sea via a pipeline, about 3 km from land. Gases are released from the plant via a number of chimneys (referred to as ‘stacks’). Discharges into the Irish Sea peaked in the mid-1970s and have dropped significantly in recent years. This is as a result of improved waste treatment facilities at Sellafield, which convert much of this radioactive waste into a solid for long-term storage.
As a result of the discharges from Sellafield, low levels of artificial radioactivity can be detected in sediments, seawater, seaweeds, fish and shellfish taken from the Irish Sea. A wide range of marine samples are collected and analysed on a regular basis by both the EA and the Manx Government. This monitoring can show where the radioactive particles become concentrated.  As expected many particles end up in sea bed sediment, so there are sometimes slight increases when the winter storms have been especially ferocious and stirred up the seabed. Generally, levels are falling from their peak in 1998. 
There are several radioactive isotopes that are monitored, Technetium-99, Caesium-137 and 134 and Cobalt-60. Of these, Tc-99 is regularly tested for by catching lobsters. Tc-99 concentrations in our local lobsters have declined from a peak of around 400Bqkg-1 in February 1998 to average 10 Bqkg-1 during 2015. These Tc-99 concentrations are lower than the levels found in lobsters caught off the Cumbrian coast. The EC recommended maximum permitted level for Tc-99 in seafood which is 1250 Bqkg-1, so these lobsters are safe to eat and regularly eating seafish will only make a minor contribution to your overall radiation exposure.
Now it’s not true to say that lobsters are immortal, but once they reach adulthood they don’t have many predators except humans. Good lobster fishery management sets minimum landing sizes for lobsters, ensuring that they are at least able to breed once before being caught. Small lobsters can get out of pots through the escape hatch or they are returned to the sea anyway.
Just as lobster pots discriminate against small lobsters, they also prevent very large lobsters from getting in.  Consequently, larger lobsters do tend to live a very long time.  The lifespan of European lobsters has been estimated at between 30 and 50 years.  Large lobsters have lived through the peak discharges from Sellafield, unlike their smaller 3-4 year old counterparts who got caught in lobster pots and tested. Lobsters have a fairly high affinity for Tc99 and they accumulate the radioactive particles in their bodies. But the only real predator for the large lobsters is, you’ve guessed it, divers. 
Something to think about the next time you wrestle a monster lobbie from under a rock