Updated: Sep 11, 2021
The joke amongst divers about peeing in your wetsuit is that there are two types of divers: those who pee and those who lie about it.
I proudly proclaim my aquatic ondinism and find it a good excuse to talk about the physiological processes that are involved with my divers. Indeed, you don't just need a wee, your body is reacting to stimulus and telling you to get rid of the excess fluids. The process is called immersion diuresis. The stimuli are immersion and temperature drop.
What actually occurs?
When you submerge your body in water it is subjected to a drop in temperature and an increase in pressure. Both these stimuli cause constriction of the blood vessels at the extremities. The vasoconstriction happens mostly in the skin and superficial tissues as well as in the muscles of the arms and legs. The remaining blood is sent to the main organs of the body, the heart, the lungs and the big blood vessels. The hormone in your kidneys that control urine production interprets this signal as a liquid overload. The kidneys then produce urine to get rid of the surplus and preserve normal blood volume. You get the urge to urinate. It’s a natural process. Once you get out of the water, the blood volume goes back to normal by drawing liquid from the tissues and muscles, so you’ll probably need to pop to the loo again then and drink lots of water to replace the fluids.
But peeing in your wetsuit, yuck!
My approach is that anything that narrows your thinking is not something you want to experience when diving. If you are thinking about holding your pee in you are probably not enjoying yourself as much, or maybe distracted and therefore unable to identify and respond to a hazard were it occurs. I just let it flow, open my wetsuit at the neck and flush it all out (some like to go upside down and purge some air into the wetsuit). I do it as soon as I feel the urge so I can give it a good few flushes then regain my warmth and have a good dive. When necessary and regularly I add some detol in the rinse tank (pretty standard in most Dive Centres) and disinfect it (thought it then stinks of detol which arguably is as bad as pee!)
(That said when diving in cold waters, flushing your wetsuit is not quite as pleasant, in fact you'll get super cold. So, in these cases make sure you have a quick pee before and after diving if you don't want pee up to your ears (when it creeps up your wetsuit into your hood, gaah))
This is another good reason to drink plenty of water (apart from dehydration risk obviously) before and after your dive and avoid any ‘diuretic’ drinks, drinks that increase your urge to urinate by interfering with the hormone in your kidneys, like coffee and tea. This way your pee is a non-offensive clear not smelly liquid.
Happy peeing to all!