Attacked by an Undersuit

Ah Autumn and a young man’s fancy turns to how to protect his delicate parts from the bracing effects of declining water temperatures.
As the leaves begin to turn yellow and the epic 3 month long ramming of Christmas down your throat begins so does the start of the drop in water temperature at the coast and inland sites. Fortunately for us the water doesn’t start to really get cold until December because the water, warmed during the Summer lags behind the air in terms of temperature. Usually the coldest time of the year to dive is January and February with October and November usually absolutely fine.

A surreptitious photo of someone diving in Vobster in January in a shortie wetsuit. note the puce colour of the skin post dive. This article is not aimed at this person.

If you really want to keep warm then you’ll need a drysuit. This isn’t just about being warm in the water it’s also really important outside because you can stay warm and dry between dives with no having to change back into a wet wetsuit which isn’t really all that pleasant even somewhere like the Red Sea. But the drysuit isn’t necessarily what’s going to keep you warm, what you choose to wear under the suit is just as important in keeping you toasty in the water.
So first of a quick recap from your Open Water Course. Many people believe wetsuits keep you warm by trapping a layer of water between you and the neoprene which your body warms up and then that keeps you warm. This isn’t strictly true. The neoprene is what keeps you warm being waterproof and full of tiny bubbles. This acts in a similar way to blubber by insulating you against the cold water. The thicker it is the more insulation you have and the longer you’ll stay warm. The wetsuit must be tight fitting because it is actually by minimising the flush through or pooling of the water that it works.
Drysuits work differently by, strangely enough, being dry. By sealing around the neck and wrists they create a waterproof seal. You then inflate the suit with air and air, being a poor conductor then insulates you. However, just like a duvet the thicker or more efficient your undersuits are the more air they’ll trap and the warmer you’ll be.
A crap drysuit

A crap drysuit yesterday

So therefore the warmest combination would be to have a thick 7mm drysuit with a big sleeping bag style undersuit beneath it trapping loads of air and keeping you warm. Except this isn’t the most practical of solutions for 2 main reasons. First off all a drysuit and undersuit combo like this is incredibly buoyant. You will probably need a metric tonne of lead to sink you. After strapping the lead on and starting your descent you will quickly find yourself facing another problem: compression. You all remember what happens to a balloon as you take it under the water, well the same thing happens to all those tiny bubbles in the neoprene and also the air in the sleeping bag suit compresses too. So suddenly you’re at depth in a suit that is now probably closer to being 4mm thick and much less buoyant with the undersuit compressed to lycra against your skin. You’re now colder than you were at the surface but more importantly you’re now hideously overweighted. Your giant weightbelt has now become dangerously loose to the point that you are currently wearing it low slung beneath the arse in the style of a hateful Shoreditch hipster.
The weightbelt falls off, you rocket to the surface and it’s exactly what you deserve for thinking Ed Sheeran is cool and only ever having one hand free because the other one is holding onto your constantly falling down trousers, you idiots.
idiots wearing saggy jeans

Some idiots yesterday

Deep breath. Anyway, drysuits and undersuits have fortunately come a long way. Neoprene drysuits are often made of compressed neoprene now, like the Bare XCD2s which give you flexibility and a bit of warmth without all the compression issues of standard neoprene. Other suits are trilaminates like the Whites. These have the advantage of being super light weight and flexible but usually require slightly more in the way of undersuits to keep you warm.
Undersuits, therefore, must be a balance between bulk, warmth, buoyancy and compression. First off most decent undersuits are made of a wicking material. This means that water coming  into contact with the fabric is quickly absorbed to the surface of the material. This is important in a drysuit because even when you’re cold you’ll still sweat and this sweat can’t go anywhere. Therefore wicking materials will stop that sweat from sitting against your skin which makes you feel cold. Cotton is useless at this kind of thing so wearing a cotton t shirt under a wicking undersuit will actually make you colder because the t shirt will just stay damp against your skin.
Fourth element have been in the diving undersuit market for years and the almost ubiquitous presence of their products at UK dive sites is a testament to how well they work. Probably the most popular set are the arctics that are now available in a 2 or 1  piece. Combined with a  xerotherm undersuit or drybase layer (they do work a lot better with a base layer) they are very warm as well as not being overly bulky.
A recent addition to the fold has been the Halo 3D undersuit. This is an amazing piece of kit. Essentially made of arctic material this has been upgraded with panels of incompressible material on the chest and thighs, these are the areas that a diver swimming horizontally experiences the most compression of the undersuit against the skin. The panels on the Halo stop this from happening and the suit really does keep you incredibly warm. There is also the added advantage of being able to sidle up to people at the dive site and whisper ‘I’m Batman’ in their ear in your best growly voice.
Halo 3D undersuit

A Halo 3D providing musculature to even the skinniest of bodies.

To put all this in perspective, I am a diving wuss when it comes to cold, the water has to be approaching body temperature to tempt me out of my drysuit but with my Halo and drybase layer on I can happily dive in 3 deg of water in winter.
You do need to wash your undersuits too, although avoid fabric softeners (easy advice for most men- what exactly is it for?) I recall a week diving in the red sea after which I came straight back to another full weekends teaching. On Sunday evening I was physically attacked in the van by a set of Fourth Element drybase layers. Fortunately I was able to subdue them, they were only disorientated and scared and reacting in the only way they knew how to their new found sentience. I took to hiding them in a shed in my garden before eventually they killed the next door neighbours daughter. After that they ran away only appearing now and again by turns to taunt me and to lament their existence. Eventually I was able to track them down to Antartica where we were both killed in an avalanche.
The undersuit attacks

Packing the kit away downstairs after a busy weekend

Anyway, the point I think I was trying to make was that now might be the time to think about shoring up your undergarments or trading that wetsuit in for a drysuit. And make sure you wash your thermals too. I’m just thinking about your safety after all.


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