You are ready to go diving and feel fine. Only moments later when the dive has just started you feel the enormous urge to pee. Not for nothing the saying goes: there are divers who pee in their suit and there are divers who lie about it. But why do I always have to pee every time I dive?
To understand te complete proces which is causing this phenomenon we first need to fully understand why we pee at all. When we drink we add water to our body. Our body has a set amount of liquid which it maintains. If the body notes that there is to much liquid it will send a signal to our kidneys. The kidneys shoot into gear and start to produce urine. When the bladder is full enough a signal is send to your brain, telling you need to pee. After you’ve done this your liquid balance is restored.
What happens when you hit the water
There is one main physical proces which is making you pee a soon as you hit the water. When you get into the water for the first time your body is pumping blood from your extremities to the core of your body. The result is that there is a lot of liquid in the core of your body. This makes the body send a signal to your brain telling it that there is to much liquid in the body. The brain signals to the kidneys which go to work immediately. Because of the high amount of liquid present in your core the kidneys will work extremely hard to produce urine to rebalance the amount of liquid. Hence you need to pee when diving.
There are two major reasons why the body is sending a large amount of blood from your extremities to its core.
Cold water Immersion Diaresis
The first reason is called cold water immersion diaresis. Whenever we go from a warm environment to a colder one, your body will react. It senses the change in temperature and wants to protect the organs against this cold and pumps a large amount of blood towards them. All the organs are located in the core of the body and by pumping more blood into the core the organs stay nice and warm. Cold water immersion diaresis is the third stage of the mammalian diving reflex and is often used by freedivers to stay long underwater.
The absence of gravity
One of the most appealing things about diving is being weightless. There is no discussion that being neutrally buoyant is important but it has a serious side effect. Gravity is quite crucial for the blood circulation in our body. When you take gravity out of the equation, the body again wants to protect the organs. It pumps blood towards the core, adding to the overall need to pee.
The whole proces is similar to what happens to astronauts in space. They also experience zero gravity and all the blood is constantly being pumped to their core. Because astronauts are exposed a lot longer to zero gravity then us divers, muscle damage can set in. This is way you always see astronauts exercise when in space. The sole reason for this is to pump blood to the extremities to keep them supplied with blood and to use the muscles which otherwise go unused.
Is there anything you can do?
The answer is simply no. The physical proces can’t be stopped and will get worse as you get more experienced. Because you get more relaxed in the water your fight or flight response will get less making you more prone to peeing. In other words, get used to it. Just make sure that you drink a lot after your dive to replenish the lost liquids. And no beer because this will dehydrate you even more.