Does water in a wetsuit help or hurt. A myth to be BUSTED or CONFIRMED

[lmorin]

Given my understanding of physics and my experiences of how loudly I scream when I hit the freezing cold water around here:

Assuming the same thickness of neoprene, I would be warmest in a wetsuit with no water in it i.e. a drysuit since the air conducts the heat away from my body much slower than water.

Next up for warmth would be semi-dry i.e. water in the suit but not flushing through. Admittedly it will pull heat away from my body pretty fast to start with but so long as the seals on the semi-dry keep the water from flushing out then once the water has heated up the speed at which it pulls heat out of my body will slow down dramatically.

Lastly for warmth would be wet suit i.e. a layer of neoprene with no seals on it. With this heat would be drawn out rapidly by the cool water and as it flushes through the suit would constantly be replaced by cold water resulting in heat being drawn out rapidly from my body.

Thats always been my understanding of it at least.

My understanding, too. Wouldn't it be a kick to learn that the primary reason thicker wetsuits are warmer is simply that they fit tighter, thereby placing greater restriction on the water flowing between wetsuit and body? Less water flushing, warmer diver.

 

[dfx]

My understanding, too. Wouldn't it be a kick to learn that the primary reason thicker wetsuits are warmer is simply that they fit tighter, thereby placing greater restriction on the water flowing between wetsuit and body? Less water flushing, warmer diver.

That's not how it works. Try a 1mm wetsuit that's one or two sizes too small (very tight!) vs. a properly sized/fitting 7mm wetsuit.

 

[Edward3c]

My understanding, too. Wouldn't it be a kick to learn that the primary reason thicker wetsuits are warmer is simply that they fit tighter, thereby placing greater restriction on the water flowing between wetsuit and body? Less water flushing, warmer diver.

I’m sorry, but that’s flawed logic.

Whether clothing is tighter or not depends on the fit, nothing to do with the thickness. Remember with Boyle's Law an 8mm think suit will only be 4mm at 10m and 2mm at 30m. The compression happens from the inside as well as the outside so the suit feels slightly looser at depth, allowing some flushing which may not happen at shallower depths.

 

[tracydr]

Once,when diving in the Puget Sound, I decided to try a thinner glove because I hated using the heavy 7 ml gloves. I used what I think was probably about a 3 ml glove with a good fit.
My fingers were numb within minutes. Thickness matters!

 

[lamarpaulski]

The reason you're wearing a wetsuit is because water is such a good heat sink... (ever see the flame to water balloon experiment ? the water removes the flame's so well the rubber of the balloon doesn't melt !) its the neoprene air/gas bubbles that insulates..like the others said a 3mm is far cooler than a 7mm..same water...also by definition the water warmed next to your skin in a 'wetsuit' does leak out to the ocean to some extent and is replaced (you can feel this in a loose suit) by COLD water so water is the undesirable but hard to avoid factor. I suppose if that initial water did NOT leak at all you would only be chilled by the effort to heat it up. I used to pour almost hot water in my suit just before jumping in once upon a time.

 

[rambaldi]

Whether clothing is tighter or not depends on the fit, nothing to do with the thickness. Remember with Boyle's Law an 8mm think suit will only be 4mm at 10m and 2mm at 30m. The compression happens from the inside as well as the outside so the suit feels slightly looser at depth, allowing some flushing which may not happen at shallower depths.

Close but not quite, a wetsuit is by no means an ideal gas and most definitely doesn't follow Boyle's law. You can see your lovely warm 7mm jacket that fit nicely at the surface and even 10m not quite stop any water rushing up your arms at 30m but it certainly isn't 2mm thick.

 

[redacted]

I’m sorry, but that’s flawed logic.

Whether clothing is tighter or not depends on the fit, nothing to do with the thickness. Remember with Boyle's Law an 8mm think suit will only be 4mm at 10m and 2mm at 30m. The compression happens from the inside as well as the outside so the suit feels slightly looser at depth, allowing some flushing which may not happen at shallower depths.

To be precise, the bubbles will compress but the rubber will not. So why does it not get shorter? Damn that rubber.

 

[Foxfish]

I’m sorry, but that’s flawed logic.

Whether clothing is tighter or not depends on the fit, nothing to do with the thickness. Remember with Boyle's Law an 8mm think suit will only be 4mm at 10m and 2mm at 30m. The compression happens from the inside as well as the outside so the suit feels slightly looser at depth, allowing some flushing which may not happen at shallower depths.

My experience is that wetsuits tend to 'cling' more the deeper you go. I think people with dry suits would find the same thing which is why you have to inflate them as you go deeper.

 

[Bob DBF]

I’m sorry, but that’s flawed logic.

Whether clothing is tighter or not depends on the fit, nothing to do with the thickness. Remember with Boyle's Law an 8mm think suit will only be 4mm at 10m and 2mm at 30m. The compression happens from the inside as well as the outside so the suit feels slightly looser at depth, allowing some flushing which may not happen at shallower depths.

As to the compression, it depends on the type of neoprene used, check out Rubatex G-231. I wish I could afford it.

My suit does not get any looser at depth than it does at the surface, of course I haven't taken it below 46m and it's too cold there to hang out for long because I can't afford the good neoprene.

To reiterate my initial point at the start of the thread, neoprene is an insulator and water is a conductor.

The reason the wetsuit has water in it is because it is cheaper to make than a drysuit, the semidry suits minimize the water in the suit and water (and therefore heat) exchange between the suit and the ocean.



Bob
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I may have been born at night, but it wasn't last night.

 

[Eric Sedletzky]

I don't have any scientific knowledge to add to the OP's original question, but I do have quite a collection of wetsuits. You might say I'm a wetsuit oficionado and collector.
Here are my personal findings using all my suits and you can interpret them any way you choose.
First the list of suits:
3 mil cheapo one piece surf suit used for tropical/sub tropical and warm lake diving - Fit is OK but has loose spots.
5/4 one piece (just purchased) and will be used for Lake Tahoe and maybe 70ish water at Catalina in Socal with a 7mm head 4 mil body hooded vest.
7mm one piece semi cheapo used with above hooded vest.
7mm camo Yazbeck freediving suit - very spongy.
7mm very dense custom built two piece hooded beaver tail commercial urchin diving suit.
1/2" (13mm) very thick Rubatex G231 custom built two piece beaver tail /w attached hood commercial urchin diving suit.

Where I dive the water ranges from 45 degrees to 53 degrees year around.

The one piece 7mm with vest fits really well because I customized it to fit perfect. I use this to clean boats and I can spend hours in the water in 6 feet and be very warm. However I decided to try it for some deeper dives and froze my ass. The material is spongy and even though it fits great the cold goes through. I get minimal cold water shock when first getting in so water intrusion is minimal.

The freediving suit fits pretty well and is skin-in (needs to be lubed up to get in). I can freedive for 6 hours in 50 degree water and be warm. A mojority of the time spent freediving is on the surface breathing up. But if that suit was to be used for scuba I'd freeze my ass in 5 minutes because it is very spongy and would be paper thin at depth. With that suit there is almost no water transfer.

The 7mm commercial suit is also skin-in and like the freediving suit has a built in hood on the top. The torso area is 14mm.
This suit is definitely warmer than the cheap 7mm jump suit with hooded vest, although the material is so dense that there are a few open areas in the suit that I can't fill such as between bicep and shoulder cap and also the indent under the pectorals and the underarms. These areas are very difficult even for a custom suit maker to cut exactly. The problem with that suit is it's so dense that there's no way to make it a bit small and stretch fit it because the material really doesn't like to stretch much. It would almost be better for a person with a good layer of bodyfat because then they could almost 'pour' themselves into it and fill the voids.

My 1/2" rubatex suit is by far the warmest. It's a two piece beaver tail with attached hood. The torso area is a wopping 25 mm thick. I've been past 100 feet with dry suit divers in 46 degree water, they got cold and I was hot.
That suit is so warm that it takes me almost the entire dive to begin to cool down and when I come up for a stop I begin to boil over again and can't wait to get out of the water to get that thing off.
Lately though I have lost a bunch of weight and now it fits a little looser than it used to. as a result it's not quite as warm because I am getting more water flow than I used to. Plus when people lose weight they tend to be colder overall anyway.
So now it's about perfect. The problem with that suit is it's so thick that shore diving is an over heated workout, kayak diving is impossible, so that leaves boat diving. It's so thick that gearing up is such a challenge even on a boat that I have limited time to get my stuff on and get my butt in the water before I start seeing stars. I've actually had to abort dives before even getting in the water due to overheating and fear of fainting or getting sick when using that suit.

I've had many other suits in the past and I can say that it's a combo of things that make a suit warm.
Minimal water intrusion with a cheap suit, the suit will be warm at first but then due to compression and loss of thickness the cold goes through very quickly.
Skin-in suits tend to be warmer because the neoprene is right up against your skin without nylon in the way to hold water, at least that is what I was told and/or maybe just my imagination.
A skin-in suit that is made out of high quality material that resists compression and fits well is even warmer.
The thickness does make a huge difference in the amount of time you can stay warm at depth before the cold gets through, but if water flows through or the suit has too many zippers
nothing will keep you warm.

So to sum up, a custom skin-in suit made out of high quality material with minimal pieces and zippers and water entry points will be the warmest style.
My commercial suits have built in hoods so I never get a cold shock down my back. They are also 3/4 zip up the front and have spine pads built in.
Adding thickness will increase time at depth before cold gets through but will add a PITA factor for gearing up and moving around topside.

There's also the training factor. People who like to dive wet are more used to cold and adapt to it.