Excessive pressure underwater question -- Feeling my legs squeezed by my waders in a stream....

Hi guys! I have question regarding vacuum and underwater pressure if anyone here could help me out with it. I'm not really a physics person (my math skills suck too much, lol), but I do find it very interesting.

I recently bought some breathable stockingfoot fly fishing waders and whenever I go into waist deep water with them, the material that the waders are made from as well as the neoprene booties compress from the water pressure very tightly onto my legs and feet. If I am just wading without the waders on, the water pressure feels very minimal, but with the waders on it feels like they are literally crushing my legs and feet. Very uncomfortable.

Underwater you can't pull the wader material away from your legs like it's sucked in really tight. There is this thing called suit-squeeze that happens to divers who wear drysuits. They have to inject forced air into the suit to prevent the water pressure from squeezing their body and causing injury. I think this is very similar if not identical to what is happening with my waders underwater, but I'm not 100% sure.

When the water pressure forces the air out of the waders or out of the suit does it in effect create a partial vacuum? Other people are trying to tell me it's not creating any vacuum, but it sure feels like vacuum pressure to me so I figured I'd ask here. I guess it's similar to how some people would put meat or veggies in a plastic bag and then place it under water to press all the air out before freezing. A type of "vacuum" sealed packaging I guess. Does this process of removing all the air underwater actually create vacuum pressure or is there something else going on here?

Thanks.

 

[jbriggs444]

I am guessing here because I do not have experience with the feeling that you report.

The inward pressure on the outside of your legs will be the same with waders or without. So it cannot be that. However, with the material in the waders pressed right up against your leg, you will feel a transverse force any time you try to move. This might well feel uncomfortable and could be interpreted as "pressure". By contrast, a pair of trousers that you wear to work is free to slide up and down your leg as you walk. And wading bare-legged, the water would also exert no transverse force.

Edit: After having undergone hip replacement surgery earlier this year, I can testify that compression dressings get freaking painful after a while.

 

[kronstadt2]

I realize this is an old post but I am desperate to find out what is happening myself, so hoping someone will respond.

Tried on new waders today, never wore waders before. I was shocked by the vacuum seal effect of the material sucking to my skin. This is an effect just like that you see out of a vacuum sealer for food. The material squeezed, tightly compressed around the legs.

I am perplexed no one except the handful of people experiencing it seems to know what we are talking about, or so my internet search's so far reveal. What we are experiencing is not tight waders (mine are quite loose out of the water) or overly sensitive skin, or circulation problems, no it is like the effect of sealing an air tight container on an airplane at altitude and then trying to open it at ground level and finding it nearly impossible to open it's compressed so tightly.

Why does this only seem to be happening to a few of us?

 

[russ_watters]

Perhaps the pressure combined with your motion (which creates forces far higher than the pressure alone) causes an extra suction effect?

Have you tried wearing pants/socks under the waders to prevent them from forming a seal to your skin?

It would surprise me if this was not a solved problem given how common waders are. Have you asked on fishing forums?

 

[DaveC426913]

Have you tried wearing pants/socks under the waders to prevent them from forming a seal to your skin?

Yes. This should help.

Why does this only seem to be happening to a few of us?

I suspect it's the same for everyone, just that others are used to it.

 

[jrmichler]

The first few times I used waders, I really noticed the squeezing. After a few times, not so much. The pressure against your legs is the same, but definitely more noticeable when using waders. My opinion is that this is due to two factors:

1) The (oversized, somewhat flexible) rubber waders compress unevenly when compared to water, so you feel it more.

2) Waders are normally used in cold water, which feels cold even through the rubber waders over a pair of pants.

Note that fresh water weighs 62.4 lbs per cubic foot, so the pressure at one foot down is 62.4 lbs/ft^2. If you shove your hand down the leg of your waders, the total force is the pressure at that depth times the area. The force adds up fast, which is why it feels like they are sucked really tight.

 

[DaveC426913]

Also, don't forget the buoyancy effect.

Any air trapped in the waders - any at all - has the net effect of making you more buoyant than you would otherwise be (because: same weight; greater volume). This results in the unsettling sensation that the waders are trying to push you up and spit you out of the water*. If you lift your feet, the waders will push up on them; it feels as if you are water-repellent. This is something you do not experience on your otherwise naked lower body.

* ^{just ask any witch}

 

[kronstadt2]

Thanks for all the replies! Sorry I didn't get back to the forum for a while. Just to be clear I was wearing heavy-weight thermal socks and fleece pants under the waders so the wader material wasn't touching my skin. Just felt like I was getting shrink-wrapped, LOL. Really appreciate the scientific explanation. I have come to the conclusion that others have the same experience, I am just surprised so few mention it.

 

[sophiecentaur]

There is this thing called suit-squeeze that happens to divers who wear drysuits. They have to inject forced air into the suit to prevent the water pressure from squeezing their body and causing injury. I think this is very similar if not identical to what is happening with my waders underwater, but I'm not 100% sure.

I get this effect with welly boots and a dry suit would certainly increase it. Why do we get the effect? he pressure at any depth has to be the same but the rubber is not fluid so that means there will be local stresses in the envelope. That could cause bruising after a while. We all evolved to cope with continuous (uniform local) pressure on our skin so the uneven transfer of force to our skin from the water is noticeable - same as if we lay on a wrinkled surface. It will interfere with blood circulation so we do something about it and move ourselves. Remember the Princess and the Pea? If you fill your wellies with water, the effect goes away!

But we do notice the effect of pressure when we are immersed. Breathing in is noticeably harder, even when floating horizontally in water and that increases with the body vertical. The diaphragm muscles are only designed to work with equal pressure on the torso and inside the lungs and we 'compare' the local hydrostatic water pressure (a few percent higher than at the surface) with the local air pressure in our lungs (which is undetectably higher than that at the surface). I imagine aquatic mammals will have stronger diaphragm muscles to deal with this; a blue whale could experience a pressure difference of, say 0.2Bar between inside and outside.

 

[sophiecentaur]

Also, don't forget the buoyancy effect.

That's due to the pressure, with a net upward resultant; when you first step in, you have to push down. When your feet are on the bottom, the net upthrust will be less, particularly on a muddy bottom. I have wasted hours of my life noticing and studying things like this! In particular I have noticed my foot gets pushed up out of the water at each step out of a deep puddle.