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There is a recent question What material is a good alternative to neoprene? one of the comments to an answer says:

whole suit filled up with water

I might be taking it out of context, but as I read the comment it seems to imply something I have heard previously that wet clothes in water are somehow significantly heavier than dry clothes on land.

Personally I have been fully dressed in the water several times. When I was in the Army we marched fully clothed in to deep water and expected to stay alive in the water (not cold) for an hour as part of "Drown Proofing". More recently I have found myself fully dressed and treading water (with a life jacket)

There is no doubt that once you get out wet clothes are heavy on land, but in water, they are just full of water, which weighs the same as water, hence it not any heavier. Often the clothes will also trap air and may add to your buoyancy.

I find that clothing also tends to keep me warmer.

How dangerous is swimming fully dressed in cotton/denim clothes?

  • Note when swimming fully clothed, I usually swim a breast-stroke as keeping wet clothes in water conserves energy. – James Jenkins Feb 26 '18 at 18:21
  • Is this situation you are picturing in cold or comfortable weather? – whatsisname Feb 27 '18 at 20:22
  • @whatsisname Comfortable to cool. Maybe 50F plus useakayak.org/references/hypothermia_table.html – James Jenkins Feb 27 '18 at 21:07
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    Depending on the material and if it is a survival situation you can also remove your pants and use them as a flotation device by tying the legs together and inflating them. The wet material holds air surprisingly well. – Nate W Mar 2 '18 at 19:17
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Cotton kills - but only when not in water. Whilst in water, cotton will not have any thermal effect. However, the material itself can easily wear you down through drag. You might be able to swim short distances, but longer ones - depending on your fitness - can slow you down considerably through drag. Elite swimmers will wear suits with soft and flowing curves, and no extraneous material. Some even go so far as to shave their body to reduce drag their hair might have. I don't know if that's effective or not, but when races are won by a thousandths of a second, perhaps it's worth it.

Clothes that are worn are not made with elite swimming in mind, and so any material - cotton or not - which doesn't easily allow water to pass through it or by it will tend to drag the swimmer, leading to early fatigue. If one were to wear tight-fitting clothes, which allows water to pass around it more easily, that could reduce that lag; but if the clothes were too tight, that can be restrictive on the muscles needed for motion or breathing.

In addition, cotton does bind to water, and holds tight to it. This is the reason we advocate against wearing cotton in cold weather, because water that gets into the fabric will have a tendency to cling to it, making the wearer colder. In the water, again, there isn't much of a thermal effect because water is in contact with the body regardless of the cotton; but the fact remains that cotton binds with water. When you are swimming, you're dragging all that water along creating additional drag. So, wearing a loose-fitting rayon shirt, for example, will have a tendency to drag the swimmer. But a similarly-fitting cotton shirt will have more of a drag effect because it holds onto the water.

Try swimming with a jacket on, and you'll feel the extra weight you're lugging around when you swim. This is a reason we call for removal of as much clothing as possible when there is a need to swim some distance. If you tread or are using a life-saving device, the clothing won't matter - and will come in handy once rescued.

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    "But a similarly-fitting cotton shirt will have more of a drag effect [than rayon/viscose] because it holds onto the water." as chemist, I don't see how the hydrophilic properties of cotton will have any noticeable effect here. The hydrophilic properties will influence the (or at most: a few) molecular layer around the cotton fibre. That's important for drying but not for the drag. Assuming laminar flow, the water layer on the cloth surface has 0 speed regardless of fibre type. Plus, rayon is chemically very similar to cotton and is similarly hydrophilic, so anyways a bad example here. – cbeleites Feb 27 '18 at 18:30
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    A cotton fiber is a tube formed of different layers. When cotton fibers grow, the inside of the tube fills with living plant cells. Once the fiber matures and the cotton boll opens up, these cells dry up and the fiber partially collapses, leaving behind a hollow bean-shaped canal, or “lumen”. This empty space holds lots of water. – Andrew Jennings Feb 27 '18 at 18:46
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    Here's some "light" reading for the "casual" reader LOL cottoninc.com/product/NonWovens/Nonwoven-Technical-Guide/… – Andrew Jennings Feb 27 '18 at 18:47
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    You can add that in addition to the drag, it affects body position in the water as well as stroke efficiency. Both will decrease time to fatigue. – JohnP Feb 28 '18 at 22:18
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    Also, yes shaving does have a large (relative) effect. This has also been proven in wind tunnels to help cyclists, and as a side effect decreasing drag is why the FINA outlawed the full body suits. – JohnP Feb 28 '18 at 22:21
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With cotton clothing the main risk is hypothermia, cotton soaks up a lot of water but also easily exchanges water easily with a wet environment, it's one of the coldest things to wear when wet. Wearing nothing is colder, but that's mostly true as long as you stay wet. Nothing dries a lot quicker than cotton, and wet cotton doesn't provide that much wind protection. Fleece is probably the best "normal clothing stuff" to get wet in, wool is heavier but still relatively warm.

Heavy clothing mostly starts being a problem in moving water. You bob up and down, but heavy clothing really limits the amount of up you can get, which leads to deeper downs. It also hinders any swimming you want to do.

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Cotton when wet can get quite cold which in turn will make you very cold or get hypothermia. Denim in my experience holds a lot of water which, like cotton, will get cold and may give you hypothermia. Also, the extra water slows you down causing fatigue.

  • Are you saying you would be colder "in the water" wearing cotton then if you had no clothing on? – James Jenkins Mar 25 '18 at 10:34
  • I think it would be colder in the water without clothes but it also does depend on the temperature of the water – Salman sadiq Mar 25 '18 at 13:43
  • Then how does this address the question? Does it add anything not already present in another answer? – James Jenkins Mar 25 '18 at 16:56
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For most people "swimming" is just splashing around and having fun in the water. If this is the case, heavier materials like cotton and denim are no more dangerous than anything else. Just take a look at a busy Midwestern lake on a summer weekend. Plenty of people are in the water not wearing "conventional" swimwear just splashing around or playing with tubes or air mattresses.

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