Dude - Where’s My Jumper? :: Tips for Keeping Warm Scuba Diving

I arrived at the dive site pretty much on time, which is rare when I’m travelling without Wifebuddy, and began to assemble my gear. For the particular dive I was using my twin 12’s, containing air, and a 7l stage of ‘shit mix’ i.e. – 29.7% nitrox.

Once my backgas and stage cylinders were sorted I began to get dressed.

The water temperature in Stangford Lough, where I was diving, was around 7C; in other words – bloody freezing. To combat these ridiculously low temperatures, I have a carefully crafted layering system; which I have honed over numerous, cold, uncomfortable dives.

As I mindlessly chatted to Dave, my drafted in buddy for the day, I reached for my tried and tested 4th Element Arctic top. My hand rummaged through my dry bag, and was greeted by … the inside of my dry bag; no thermal top.


Having subsequently received a look of, “Oh you’re going to be cold fella,” I swiftly delved into denial, and turned the jeep upside down in the vain search of the elusive jumper. Of course, I knew immediately upon discovering its absence, the top was hanging up ‘to air’ in the scuba room.


my "Nile" hoodie
I still had some layers up top, and opted to use the hoodie I wore in transit as a substitute for the scientifically created thermal undergarment.

I managed a 55min dive. Initially I was cold. At the end I was fucking *foundered.

*foundered: A Northern Ireland colloquialism referring to a level of hypothermia resulting in male genitalia retracting fully into the body.

This is not a widely know expression.

It caused my TDI instructor extreme confusion when he surfaced shivering, and I asked; “Are you foundered?” 
He explained he wasn’t sinking. That confused me.

24 hours later I am still cold, may be developing a cold, and don’t want to be cold every again.

Usually my dives are completely comfortable, even in such low temperatures.So, here are few things that may keep your dives nice and toasty. Well, perhaps not toasty; but certainly not as cold as it could be.

Why do scuba divers get cold?

The science behind this is relatively straight forward. When scuba diving, the divers body heat is lost to the water; water carries heat away 25 times more effectively than air.

The longer a diver is in the water, the more heat the body loses; thus getting colder by the minute – ending up “foundered.”

So, how can we protect ourselves?

How to stay warm scuba diving

Thankfully there are many options to prevent the foundering. Here are some of the things I have learned diving in waters down to about 6C. Of course many divers experience much colder dives, but the principles are the same. 

The biggest problem, when protecting oneself from the elements, is that every human being has a different tolerance for the cold. What keeps one diver warm will often leave another in initial stages of hypothermia.

Being cold when diving can be extremely dangerous. Hypothermia can set in more easily than most divers realise, increase blood pressure, and in extreme cases lead to unconsciousness, or even cardiac arrest.

Extreme cold can also have negative effects on decompression models and off gassing.

So, here a few tips for cold water diving:


Proper preparation prevents piss poor performance!

  • Ensure body temperature is maintained prior to the dive - If you are cold before the dive, you are certainly not going to get warmer once you get in.

  • Eat properly before the dive so that the body has the necessary fuel – the amount of energy expelled when cold is very high.

  • Wear a hat at all times. The majority of body heat is lost through the head. I wear a beanie up until I don my hood.

  • Pre-build kit: If possible set your kit up at home. As a result when you get to the dive site you are not faffing about in the cold putting things together.

In short; anything you can do to minimise the time exposed to the elements before the dive is time well spent.


My Oceanic Shadow Semi-Dry

  • Ensure a correct fitting suit

  • Wear a shortie over the top of full length suit

  • Use a thinner neoprene rash vest next to the skin under the main suit: 1mm titanium vest or similar works well.

  • Neoprene socks under wet booties

  • Ensure hood is 7mm or thicker and is tight fitting

  • Consider mittens rather than 5 finger gloves

  • Priming suit with warm water – flood the suit with a thermos of warm water

  • Keep your hood donned post dive, and keep it on until getting changed into dry clothes.

  • Diving wet has limitations, be aware of your dive time and avoid decompression obligations.


My Seaskin Dry Suit w/ Dry Gloves

  • Wear appropriate undergarments; avoid cotton as it causes sweating when worn next to the skin.

  • Merino base layer: merino wool is excellent as a base layer as it absorbs sweat. It also displays natural anti-bacterial qualities which stops the “dry suit stink!”

  • Layer up: Layers trap air, and air keeps the body warm.

  • Consider dry gloves: Dry hands are warmer than wet ones in my experience. If dry gloves are used consider 2 layers of liners. I use a merino liner with a thinsulate over the top – my hands are always warm.

  • Wrist warmers: The area at the wrist seal is susceptible to heat loss, as the blood vessels are very close to the skin. I have found wrist warmers under the latex seal make a significant difference. (These only work with dry glove systems.)

  • Bibbed hood: If the dry suit has a latex seal, a hood with a bib is an excellent addition as it will provide insulation around the neck which is otherwise only protected by latex. Many suits come with a neck cover that the bib can be tucked under for extra warmth.

  • Wear undergarments to the dive site: I have found getting changed into my undergarments at home preferable to a freezing car park at the pier, or shore. This means I arrive at the site warm and ready to go.


  • Keep moving: as my diving ability improved I noticed I was becoming colder on dives. This was due to the fact I wasn’t fining about as much in order to compensate negative buoyancy, or bad trim. It sounds daft; but I’m so fabulous - I’m cold.

    I counteract this by, every now and again, fining a bit erratically. Wifebuddy and I spent our last dive displaying some rather spasticated techniques whilst travelling in shore.


It is critically important to be aware of temperature when diving. When the core becomes cold, the body draws heat from the extremities as a counter measure. If you notice hands and feet starting to get chilly it’s a sign your core body temperature is dropping.

Never be afraid to signal if you are cold during a dive, it is an important factor that shouldn’t be ignored.

If you feel cold, your body is trying to tell you something – listen to it.

Stay warm and safe diving folks!

Do you have any other tips for keeping warm?

PS – There is also the doormat method of keeping warm; but I’ll let you find out about that on your own. J


  1. I've used anonymous because unsure of other profiles. Good blog. One question, at what temperature could you get away with diving in a wet suit in northern ireland? never used dry suit before.
    p.s. nice definition of foundered

  2. Hi Hugh,

    I dived wet in NI for a couple of years. I could do 40 mins at 10C no problem.

    Once below 10C i found i had to shorten my dives a bit.

    I dived Portroe quarry (IRE) in 7/8C and was completely foundered. It wasn't a pleasant experience, and one i haven't repeated!

    10C is my personal 'wet limit' over here, although i regularly dive with a couple of guys who only own wet suits. They manage 30-40mins in winter in the Lough.

    Sorta thing you just have to try and see to be sure.

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Thanks for commenting, I appreciate it!

Safe diving buddy.