Photo ©Jari Ilmonen
Winter diving is magical at its best: quiet, clear and calming. But. If the cold creeps in between dives or the equipment doesn't support the conditions, the feeling quickly turns to the "never again" department.
The good news: a lot can be done by making sure the basics are in place .
And once they are in place, you can consider technology (heated vests, argon) as a final fine-tuning - of course, for a crew doing more demanding technical dives and/or significantly longer dives in cold conditions, then of course it is wise to have all the tools at your disposal. Note that the focus of this article is on recreational and fun diving in cold conditions.
1) Dressing: warmth is built in layers
In drysuit diving, thermal management does not necessarily depend solely on a good base layer, but on the whole. For example, DAN describes a drysuit diver's thermal protection as being based on layers (base layer → insulating layer / base layer → protective layer = actual drysuit, no matter what material it is made of) and the right kind of insulation for the conditions.
Start here: base layer
- Choose a material that wicks moisture away from the skin and works in the cold (many like merino wool, some prefer technical sports layers).
- Goal: the skin surface remains drier → less sensation of cold.
- Wear as many layers as you feel you need - but avoid stuffing yourself into a cocoon: this can make it difficult to move around, and you also need some space for insulating air.
Then the most important thing: an insulating undersuit
- Thickness and insulation are selected based on water temperature and dive time .
- When the underwear is warm enough, you feel comfortable and the cold doesn't suddenly strike.
- In addition to the thickness of the underwear, the material is of considerable importance: the products of the brands that dominate the Nordic market are suitable for the conditions. The insulating fiber must be such that it allows insulating air between/inside it, cf. Ursuit's Finnfill. On the other hand, many manufacturers also use different materials and technical solutions in their suits so that the suit does not collapse under pressure, but instead leaves a suitably airy, insulating layer between the cold water and the diver.
Keep your head warm.
- A dry hat on the surface immediately puts it on your head.
- A hood that is thick enough for when in the water (or a dry hood if that's your thing).
Surface chores: don't let the cold in
- Take extras with you on your trip: dry change of clothes (including a hat, gloves, socks).
- Keep your breaks warm so you don't get cold before the next dive.
2) Eating, drinking and resting: warmth from within
In the cold, the body spends more energy, and when you're tired, you get cold more easily. It's also easy to forget about hydration in the winter, even though it's just as important as any other time of year.
Previous day
- Eat properly: and I'm not specifically referring to anything bad, but proper and adequate nutrition would be great.
- Good hydration is built up all the time, so if you see a place for yourself here, start preparing the day before - it makes it a lot easier!
Diving morning
- Eat a nutritious breakfast (well-known examples: porridge with good fillings + egg / bread with various fillings, etc.).
- Avoid anything that makes you feel uncomfortable in the water, burps/heartburns, etc.
Lunch for a diving day
- Hot, spicy soups in a food thermos are practical: easy to sip in moderation between dives. The author also recommends pea soup, which is a great snack - and as a joke, it also helps with gas. Seriously : if it causes stomach cramps , then it's probably not worth it.
- Small doses throughout the day → warmth and energy without gas or heartburn in the water.
Hot drink + hydration
- Coffee and snacks are highly recommended if you like them, but also remember to bring water/some hydrating drink.
- Hot blackcurrant juice is a classic for a reason: warm, easy, effective, good. The hot juice in a thermos is warming and, unlike the liquid in a plastic bottle, it doesn't freeze so easily during a dive.
Rest
- Try to get a good night's sleep, especially before a winter dive day. When you're tired, you feel the cold more easily and your decision-making may be impaired.
3) Once you have the basics in place: thermal vests, heated underwear and argon
This section is intentionally last. Many people spend a lot of money and time on technical solutions and their specs, even though the biggest benefit often comes from the base layer, underwear solution, and surface warmth.
Thermal vests and heated underwear
DAN reminds that not all heated clothing is intended for underwater use , and that you should follow the manufacturer's instructions and only use one that is designed for diving purposes.
Good basic logic:
- Try first : layers + underwear + body warmers + snacks/rest.
- If you're still cold: a heated base layer/vest can help.
Drysuit bulkhead + battery
This is a common and effective method when the whole thing is intended for it and installed correctly (manufacturer's instructions). The most important thing is safe use and that the system is specifically designed for diving use. DAN's article has a pretty good article about this.
Note: there is some debate about active heating systems and decompression risk (heat can affect physiology at different stages). If you are using active heating in more technical profiles, please carefully review best practices and use conservatism.
In Depth Magazine published an article on the topic in 2021, including one written by DAN expert Reilly Fogarty, if you are more interested in the topic.
Argon as a drysuit filling gas: when should you consider it?
Argon is a less poor conductor of heat than air, and has therefore been used as a drysuit filling gas in cold conditions. In studies, argon has been shown to be a better insulator than air in drysuits in some conditions (and the effect has also been examined in cold water dives by the Finnish Defence Forces).
When should you consider argon?
- When you already have:
- good base layer + sufficiently warm underwear
- sensible outerwear and warm clothing
- good food, hot drinks and rest
- and yet you freeze (or dive in really cold weather for long periods of time)
- And of course, it's a completely different matter if you use a separate gas cylinder for one reason or another, then you can of course have air in there, but why not also argon, if that's possible/reasonable.
The most important safety point in practice:
Argon is only used for filling dry suits , not as a breathing gas. Therefore, the argon setup is done with a separate small cylinder and a reducer-gauge-hose set specifically designed for filling dry suits.
Finally, the checklist in a nutshell:
- Dressing properly (layers → underwear → warm head & stay warm on the surface)
- Eat, drink and rest (anticipation + warm snacks + hydration)
- When nothing is enough (or your operations are such that any additional heat supports safety) then technical assistance (e.g. heated underwear)
- The same thing applies to the use of argon.
