Why Do We Pee After Diving?

Why Do We Pee After Diving?
– Credit: Kryvenok Anastasiia

Ever had to pee after scuba diving? You’re not alone, and you can thank (or blame) the pressure!

Most divers have tried it at one point or another, and most experience it quite frequently: after coming back from a dive, they’re overwhelmed with a need to pee.

But why the urge to pee after diving? Why does scuba diving and urinating go together?

Well, as with most things in scuba diving, it has to do with pressure.

It also has to do with the heart making a mistake!

Pressure at depth

Water is more dense than air, more than 800 times more dense, in fact.

So when we dive, that pressure exert itself on our bodies.

This is the reason for many of the things we have to deal with in diving; equalizing our ears on descent, watching our depth and time to stay within no-decompression limits, and many other things.

Here’s why you should Know Your Air Consumption.

The pressure also means that the normal effect of gravity is to some extent suspended, which is why we can float at the surface, or hover at depth. 

Divers hover as pressure suspends gravity
Divers hover as pressure suspends gravity
Photo by: Jon Milnes

The heart knows

In the human torso, in particular around the heart, we have a series of receptor, essentially sensors, that can detect the levels of fluids in our body.

The level of fluids, as in blood and water in our system, has to be kept at a fairly narrow spectrum for our bodies to function optimally.

If we don’t have enough, our bodies react by attracting water from our extremities, i.e. arms and legs, and will signal to the brain to introduce more water, which is why we get thirsty.

If we have too much liquid, the same sensors tell the kidneys to expel excess liquids by producing more urine.

Are you Getting Fit For Diving?

The heart doesn’t know

However, when we dive, the pressure of the water coupled with the decreased gravity, means that fluids from our extremities are pushed back into our torso.

Usually, gravity ensures that a good portion of fluids are kept in the arms and legs, which is the reason our feet can swell up when we walk around a whole day or sit in an airplane seat on long-haul flights.

But the lack of gravity reduces this effect, and the push of the pressure further drives the fluids into our torso.

Lack of gravity underwater pushes fluids into our torso
Lack of gravity underwater pushes fluids into our torso
Photo by: Elisei Shafer

This is actually good for our extremities, but it also produces a situation where there’s are suddenly more fluids in our torso.

The receptors pick up on this, and interpret it as if there’s an excess of fluids in our system and do what they always do in that case: trigger our kidneys and produce more urine.

They basically make a mistake, though an honest one.

Once we’re back on land, gravity and pressure is normalized, and the fluids return to our extremities, and the extra urine production ceases.

However, whatever urine is already produced still need to go, so to speak.

Cold water tends to emphasize this effect, which also explains why diver more often find themselves needing to pee after a dive in low temperatures, than in tropical conditions.

What goes out must come in

The excess peeing caused by diving, is one more way that our scuba diving causes bodies to dehydrate (the others being breathing very dry, compressed air, and general activity).

So it is important, in particularly with repetitive dives, that you replace the lost fluids by drinking extra water.

If you find yourself feeling nauseous or with a headache, you may already be quite dehydrated, and should suspend diving for a little bit, rest in the shade or a cool location, and drink plenty of water or sports drink to replenish your body.

This is where Making A Dive Checklist becomes handy.

On repetitive dives, replace the lost fluids by drinking extra water – Credit: Public Domain
On repetitive dives, replace the lost fluids by drinking extra water – Credit: Public Domain

To pee or not to pee

Of course, this whole thing leads to the debate of whether or not you should pee in your wetsuit.

Some think it is horrific and should never be done, while others claim there are only two kinds of divers: those who pee in their wetsuits and those who lie about it!

In any case, urinating under water isn’t problematic (it doesn’t attract sharks, for instance, as some claim) and can be done in a wetsuit.

Here are some of those Diving Myths.

For long dives, in particular technical dives, it may even be necessary.

However, from one diver to another, please only pee in your own wetsuit. Peeing in a rental or borrowed wetsuit is really just bad form.

Have you ever tried peeing in your (or a rental) wetsuit? 

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