How warm is a Dry Suit ?

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France / Switzerland
# of dives
200 - 499
Ok the following question is highly subjective but here goes..

1 : We dive weekly in cold water, it's summer here but at 30m it's around 8° with a surface temp around 24°.
2 : We have never dived in Dry Suits.
3 : We normally wear 7mm wet suits with 3mm Neoprene T-Shirts underneath, gloves, hood, boots etc..

On a typical dive we would spend around 20mins or so at 25m -> 35m , decos limited to around 5m.. At around the 20 minute mark the cold definately starts to become disagreeable and we want to rise to a warmer depth...

We are seriously considering the "investement" in SF Tech Dry Suits, they are local and most importantly custom made...

My question is as follows, even though it's subjective :

Do drysuits actually keep you warm or do they just inhibit the cold for a longer period of time ? Is it comparable to having good quality skiing gear, we ski a fair bit and have good gear and almost never feel the cold even when it's getting down to -10°. ( uncovered skin is obviously the exception). With skiing we have three layers, the first layer being thermal underwear, 2nd being a shell jacket, 3rd is your skiing jacket ( a standard setup for the alps). I had pretty cheap skiing clothes in the beginning and I would suffer on the very cold days.

My question is under the assumption that we would be wearing proper undergarments, let's say 300g as an example. If we head down to 35m and it's 8° as usual what would we likely feel compared to diving in our wetsuits. Obviousy the head and hands will feel the cold first as they are the least protected, (hands could be debatable depending on dry or wet gloves). Will the body, legs, arms and feet still feel the cold, I would presume and hope that it would be "much" less or are we so well insulated that it can almost be ignored ?
On a normal dive my wife gets colder far quicker than do , but has very little body fat, almost no natural protection. I can usually gain 10 minutes on her before I start to notice cold discomfort. I understand that it will be different depending on body size etc..

What would be a good comparrison, is my skiing fitting as a comparrison, if not what other examples would be demonstrative of the difference between dry and wetsuit warmth.

The SF Techs are expensive and I am having second thoughts if the price justifies the return.. ( The same goes for any other of the high end dry suits, SF Tech is simply our choice because it's local)
Being warm and being dry two completely different things, you can get hypothermic while remaining completely bone dry and you can be pretty cozy while still wet.

Trilaminate suits just keep you dry, warmth comes from layers of undergarments. That can be either passive (just layers of clothes) or active (heated stuff), mostly combination of two.

Neoprene drysuits keep you warm and dry as well but not my cup of tea so leave it to someone else make suggestions.

Look at your local divers what they are wearing, could be some difference based on yours versus theirs cold tolerance however you will probably need (give or take) something similar.
you lose heat 20x faster being wet so even with a good 7mm its not as efficient as staying dry, you'll notice the dfferance on the second dive- after surface interval wet suit divers seem to feel the cold more on the second run compared to a dry suit diver - as stated warmth come from the inner suit rather then the outer shell - get a good one dont buy a cheap one, nothing worse than a leaking dry suit
It's all about the underclothes. Look at the Santi BZ400 for example.

Also the built-in heating, essential for decompression dives.

And dry gloves.

You're never going to be toasty warm in cold water, but with good undersuits and heating you'll not be cold.
Dry suit omg is beautiful, completely different feeling by staying dry. Come to Cozumel in January and February, I might be back in mine for afternoon dives
I think the skiing comparison is apt. It is a bit like that - a good undersuit will keep you warm for a while. Also similarly to skiing you will get cold in the parts of your body still exposed, the face for example.

What is significantly different from skiing is that you’re doing very little physical activity and hence you will generate less body heat and tend to get cold faster, or at least inevitably over time, regardless of the undersuit… unless you bring heated vests and stuff into the equitation, where I have no experience.

That said, 8C isn’t *that* cold, I can easily be down 45-60 minutes in that or colder with just standard passive undies.
It's important to say that the type of diving you do can affect the type of drysuit you select.

Technical divers -- those that do long, multi-hour, dives in the cold -- tend to favour membrane suits with drygloves, heating, thick undersuits, etc... This is expensive stuff; could easily spend $5k or more, the battery's very expensive.

If you're mainly doing recreational type dives of say an hour or so, then you can look at neoprene drysuits such as the excellent O-Three drysuits. These have some intrinsic insulation and need thinner underclothes. A good quality O-Three is a lot cheaper than a membrane suit with all the bells and whistles.

I will not dive without plumbing in a pee valve. Age plays a part here but I wouldn't even think of jumping in for two hours without being able to pee.
There's so many variables to diving dry. Type of dives, undergarments, dry gloves vs wet. I MUCH prefer dryto being wet.

Example; I'll dive for 2+ hours in 35f water looking for oysters, but I'm working. I could maybe do 60-70 min if it was a leisure dive and that cold. I can only do about 35-40 if I'm dead still.

The best thing is you can modify your undergarments to suit your needs.. little cold? Add something. Little toasty? Take something away. You'll just have to feel out what works for you. Having a background in skiing and layering up will be a huge benefit to you.

I dive a used neo drysuit with marino wool base and 4th element undies when it's cold with dry gloves and a P valve. (Just for clarification). I dream of a trilam one day,but my suit is good for local muck diving and getting down and dirty.

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