Who has never peed in his wetsuit is truly a Superman ! New divers often wonder why they are seized with an irresistible urge to urinate when they are underwater. Is it due to a faulty bladder or excessive drinking? No, the reasons are simply physiological.
The low temperature of the water
Like all mammals, humans are warm-blooded (their body temperature must be maintained at 37°). When immersed in fresh water, the body cools down and then, it will make every effort to prevent this heat loss. By decreasing blood circulation in the limbs and skin, it causes a rush of blood to the heart. The body also secretes a molecule, the natriuretic peptide that acts on urinary elimination while the hypothalamus reduces the production of an antidiuretic hormone. These mechanisms result in diuresis (urine production) six times higher than normal because the kidneys are highly stressed, which explains our desire to urinate. In addition the excessive water pressure on the diver’s body also accentuates this phenomenon! 
Should divers avoid drinking before diving?
This increased renal elimination increases the desydratation of the diver who loses around 1 liter of water during a dive, it is essential to drink before and after each dive. Not doing it can put yourself in danger, dehydration increases the risk of decompression sickness. ! Last tip, remember to rinse your suit once out of the water or equip a dress with an opening to be able to quietly pee into the sea. Please do it at least for the poor divemaster washing all the equipment 🙂
