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.

​At the end of 2016, diver training agencies including BSAC launched Sea Survival training courses developed in conjunction with the RNLI. Despite the common view of the RNLI as being the provision of lifeboats and crew, there is much more that they are involved in from a safety at sea perspective, with particular foci on fishing industry accidents, Swim Safe training courses and safety advice for all water users. It’s astounding how many fishermen don’t wear lifejackets, especially local pot-boat skippers who often work alone.
To try to educate fishermen the RNLI brought a dozen of them from around the UK down to their training base in Poole. All the skippers had previously attended the mandatory Personal Survival Techniques course (and it’s predecessors) which are run in swimming pools around the country. The RNLI trainers asked about lifejackets and got the usual story, the fishermen had them but rarely wore them. The general feedback was that as strong swimmers they were confident that should they fall in the sea, they would be able to swim back to their boat, climb up the tyres on the side and self-rescue. Interestingly, qualified divers and anyone who swam in the sea was excluded from the test group. Repeated attendance at sea survival training had led each fisherman to conclude that their lifejackets weren’t necessary.  The RNLI sought to challenge that belief.
The night before the training course, the trainers opened the doors around the training pool to let out the heat. Overnight the water temperature dropped to 15 degrees.  If you are a diver around the British Isle I am sure there are days where you dream of 15 degree water! At the first attempt the fishermen were asked to wear their normal deck attire and jump in to deep water to simulate falling off their boat. With no life jackets on, the impact of cold water shock was immediate. None of the 12 fishermen lasted longer than 5 minutes before a rescuer intervened. Post dip interviews revealed their shock and surprise at how debilitating the cold water was, definitely nothing like their sea survival training course.
Cold water shock is an immediate short-lived response to immersion in water less than 15 degrees. Blood vessels at the skin contract rapidly, increasing blood pressure and the heart rate. An initial gasp for air can be followed by a breathing rate that is 6-10x higher than normal. It is likely that cold water shock accounts for most deaths when people have unexpectedly entered the water. If you are not wearing flotation during this phase, keeping your head above water becomes the biggest problem.  Over the next 10 minutes, cold incapacitation reduces blood supply to the muscles, making it difficult to swim or self-rescue. A crew member throwing a life ring to you during this time will be frustrated that you can’t actually hold onto it or kick towards the safety of the vessel.
The following day the exercise was repeated but this time with lifejackets being worn. The same cold water shock reaction was initiated, but the fishermen didn’t have to work so hard to keep their airway out of the water, the cold incapacitation stage took longer therefore improving their chances of getting back to the ladder on their boat. You can see the videos from this exercise on the RNLI website.
This started me thinking about why divers were excluded from the test group. I’ve realised I still brace myself for the cold water after decades of diving. OK, I’m wearing a drysuit and the cold water shock reaction is pretty much limited to my head and hands. But how many of us drop beneath the surface in anticipation of that brain freeze moment? As the blood vessels rapidly contract they stimulate the trigeminal nerve sending pain signals to your brain. It hurts for a few moments until you become acclimatised. The fishermen in the RNLI training exercise couldn’t get past that brain freeze feeling.
I think we sometimes underestimate the impact that cold water immersion has on new divers. I can recognise it enough now, but when I think back to learning in a wetsuit I can remember the feeling of panic, rising heart rate and accelerated breathing rate as I used to get into the water. Although we will all recognise increased air consumption by trainee divers, perhaps part of this is their reaction to cold water immersion? I’m sure that with experience comes the anticipation, the forced control of breathing rate for the first few seconds, but until our new divers have developed their response, maybe we should keep a close eye on them for those first couple of minutes? If your trainees are hoofing through their air and their buoyancy is being disrupted by their rapid breathing rate, maybe it’s something to consider?

​Once upon a time my Editor and I went diving together.  It was a few weeks after he had penned an opinion that back entry dry suits were an integral part of the buddy relationship.  It was, he opined, important to trust your dive buddy to close the ridiculously expensive brass zip without trapping your undersuit or that annoying flappy bit of neoprene stuck in the back of several suits.  Relying on your buddy to ensure the zip was closed all the way, contributed to the mutual support aim of buddy diving.  As we stood kitting up for our dive, I happily fastened my front-entry plastic zip with the minimum of fuss and decided to tackle Simon about his ill thought-out piece. 
I have a front entry suit because I like being responsible for myself…or more precisely I don’t always trust my buddies, especially if my buddy is a trainee or new to dry suit diving.  I lack the ability to rotate my neck like a barn owl to check that everything is OK behind me.  It only takes one trainee, who earnestly assures you that the zip is closed when in fact it’s half an inch open, to make you reconsider.  When that cold rush of sea water starts running down your shoulder, you know that this is one mistake you won’t be making again! 
But how do you get the dive manager or boat crew to double check your zip without offending your buddy? Surreptitiously sidle over to the crew as you leave harbour, keep your voice low so it can barely be heard above the engines (and definitely not by your buddy) and assume some wistful position that doesn’t look like you’re hugging a large imaginary tree?  And of course all the while you must try not to offend your buddy and generate “trust issues” because at the very first time you are supposed to rely on their assistance you bailed and found another source of help.
So for me a front entry suit solves all of these problems.  If my zip isn’t closed properly, then that’s my fault and my soggy right leg. For anyone thinking of getting a suit with a plastic dry zip, they are fabulous but never ignore the need for silicon greasing the stop end, even between dives if you’ve peeled out of your suit. But it’s my responsibility and I’m good with that.
Front entry suits frequently have two zips, the dry one and a cover zip, and this can cause endless problems too.  I took my eye off the ball one day whilst doing a dry suit introduction in the pool.  I will accept some of the blame, but we had just done a session at the dive centre trying on suits, and the concept of a dry zip and a cover zip had been discussed as we established that this particular suit was a good fit.  I am to blame for thinking that our discussion would be remembered barely an hour later when we kitted up on poolside.  When I turned to look at my two eager divers, they had closed their zips and were ready for the stride entry. Yes, the cover zip was closed.  No, the dry zip wasn’t.  Yes, the suit filled with water (luckily the warm pool version). No, the diver couldn’t climb up the pool ladder unaided. The phrase “I seem to be getting a little wet” was a total understatement on her part.  Once dekitted, we laid the unfortunate lady down and rolled her around on the pool surround to empty the water.  To give her credit she laughed nearly as much as we did and gamely carried on the orientation session. Five years on she is still diving, in a front entry suit, which she knows has two zips and one of them is very important.
Sadly she’s not the only one who’s been caught out in this way.  Even some quite experienced visiting divers have missed the ‘hard to do up’ brass zip and relied on the ‘easy to do up’ cover zip in one of our rental suits.  A cold shot of Irish Sea water down the leg is a salutary lesson in the need to familiarise yourself with hired equipment.  So for anyone who read, noticed and remembered Simon’s treatise on the importance of back zipped suits for buddy trust and diving, maybe I was wrong to criticise him and perhaps divers with front entry zips could do with their buddy’s assistance, just sometimes. 

The beauty of running a dive centre is that we become the first port of call for the ‘odd projects’ that come along.  Over the years this has varied between organising dive conferences, running evening snorkel safaris, recovering plankton data recorders, surveying scallops, razor shells and caves, and every so often some film work. A while ago I worked with a German film presenter whose task was to catch and cook some scallops.  Part of the director’s vision was that the poor presenter didn’t know the plan until she arrived on the shoot.  This is a European programme so she’s seen Belgian chocolate factories, Swiss cheese makers and now she was headed for the bottom of the Manx sea bed. 

In situations like this your Instructor Sense starts tingling as bad as Peter Parker’s Spidersense ever did.  How much diving has she done? Has she dived in cold water before?  Has she used a dry suit before?  Has she ever used a full face mask and comms?  The director shrugged the questions off with an air of nonchalance that only a non-diver could maintain.  Would it be alright if they flew in on the Saturday morning, did the filming and flew out in the evening?  Involuntarily my hand flew up to smack my own forehead as I briefly lost my air of professionalism.  Cue a lengthy discussion about sea conditions, weather, familiarisation with new kit and skills, risks of DCI and flights. Oh and the scallops in question being out of season at the time they wanted to film, making us liable to a fine of £50,000!

The Director of Fisheries was duly contacted and issued a special permit for us to collect and retain enough scallops for the filming.  The TV director was persuaded that a three or four day filming period was needed to be able to teach his presenter the necessary skills, safety divers were lined up and we started anxiously watching the weather.  I read somewhere the other day that many teenagers wake up and check their Facebook profile before getting out of bed, brushing their teeth, using the toilet or anything else.  I’d like to think I’d never be that bad, but I’ve realised lately that I can find the weather apps on my iPhone before I’ve really opened my eyes in the morning.  I’ve become a compulsive forecast watcher.  And as filming days approached the weather was looking less and less favourable.

We took the executive decision to go and catch our scallops early and store them so that we would at least be able to ‘seed’ a sheltered bay if the weather really turned bad.  As the scallop season had closed in June we hadn’t bothered going near our favourite scallop spot over the summer.  We dropped down in anticipation and were stunned by the state of the seabed.  Port St Mary Ledges are a series of limestone gullies running out from the shore.  Although the dredgers run up and down the sand at around 30m, they never usually come into the rock ledges – but that must have changed last year.  If we’d sunk a tractor and ploughed the seabed it couldn’t have been any worse.  The deep gouges through the rock and sandy gullies had cleared every bit of life; the hydroids, dead man’s fingers and sponges had all been ripped away. And there were no scallops at all.  Luckily our back up plan for a slightly deeper, more tidal site came through and we collected our scallops for the shoot.
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The shooting days were long and repetitive.  The weather was as bad as predicted and the visibility was poor.  Our safety divers ‘seeded’ the seabed from the bottom of the shot line.  Never before has a skipper so confidently said “Head North and you’ll find the scallop bed.”  But our presenter wasn’t happy.  The overwhelming amount of new skills and new kit, the demands from the director and film crew and challenging surface and underwater conditions tipped her over the edge.  For a couple of hours she sulked in the cabin next to the heater, declaring that she had never been so cold and miserable in her life.  Never underestimate the power of divers to ‘make things happen’.  We dressed our male dive intern in the female presenter’s drysuit, gloves, mask and hood, dropped off the back of the boat and went and did some more filming anyway.  The dive brief was short and sweet and mainly consisted of reminding him “Don’t look into the camera” repeatedly!

I want to dive all year round.  I’m not addicted to diving, of course.  I could give I up any time I want.  It’s my choice to have the kit and the training that allows me to be out whenever the conditions permit.
I started out my diving career in a wetsuit, a badly fitting, compressed, slightly smelly dive centre wetsuit.  It wasn’t described to me in those terms of course – it was a semi-dry suit, which is a term that has always puzzled me.  Semi-dry must by definition be semi-wet and how wet do you have to be before you are just wet?  Maybe my approach to life is too scientific but wet and dry are opposites and in my world ‘damp’ is still a form of wet.  So there I am in a wetsuit.  On my 9th dive, whilst on a diving course, I had my first hit of hypothermia.  It was a sunny day in Cornwall, but an old and poor fitting wetsuit was enough to make me cold in the water and then the wind chill back on the boat sapped my remaining core temperature.  I just remember feeling extraordinarily tired as I huddled down into the bottom of the RIB and passed out.  It took 3 or 4 days before I felt well again and the experience was enough to send me off to find out about the dangerous world of dry suit diving.

My Diving Office at the time thought that drysuit diving was best left to the experienced guys so his ruling was that only Sports Divers with at least 2 years diving could use drysuits.  (And just in case you were wondering, yes Nitrox was the devil’s gas.)  I went outside the club for my training and have never looked back.  The first training session wasn’t auspicious. Despite the 5am arrival at Stoney Cove we still didn’t manage to get into the water until after some other divers had been in and come out.  The water dripping off their kit froze on the path and my buddies and instructor slid elegantly down into the water.*  The instructor I was diving with provided a membrane suit without any undersuit, but I was reassured that hiking socks, tracksuit bottoms and a long sleeved t-shirt would be fine.  The sweatshirt I’d brought was a layer too far and would have “doubled the amount of lead” I was carrying, so it was left in the car.  Needless to say I was freezing during and after the dive.  Inversion drills aren’t funny when your feet come out of the suit boots but I was so cold that I didn’t notice until I tried to fin.  It seems funny now, but as an instructor I would be mortified if I had taught such a poor course.  Half the students in my group gave up diving totally shortly afterwards!

So now I am an instructor I am acutely aware of hypothermia.  We’re taught on instructor courses that your kit as an instructor should mirror your students.  All of my instructor team wear dry suits, so it’s natural that so do our students.  Besides, there’s no point trying to teach someone whose only thoughts revolve around wanting to be somewhere warmer.  Our students not only get drysuit training but proper undersuits and socks as well.  We explain the cooling properties of sweat on cotton t-shirts and frown on those who keep mentioning that their mate in [insert name of a.n.other UK diving location here] has just been learning in a wetsuit – and they said it was sooo much easier.  Less dives and less to remember.  And ultimately less diving too!

Around the Isle of Man the sea hits it’s coldest at the end of February, beginning of March.  Over 120 years of continuous data recording at the sadly closed Port Erin Marine Lab have shown this to be the case.  It’ll bottom out at around 4 degrees and dry suits become essential.    Every so often the devil inside me offers the newly qualified diver with the ‘mate who learned in a wetsuit in the Irish Sea’ the chance to do a wetsuit dive.  That is usually the end of the topic and within a couple of weeks they’ll be in the dive centre being measured up for their drysuit.  This ensures that they too have the kit for that year-round hope that the wind will stop blowing, the swell will subside and the vis will superb. They join me in the ranks of fevered weather watchers just looking for the gap in Atlantic low pressure systems. The winter storms have stripped the kelp off the rocks now and this breathes a whole new perspective into our favourite sites.  Maybe I am addicted to diving. Winter diving?  Bring it on!
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*I lied about the elegant part.