There are two types of diver - those who pee in their wet suit and those who lie!

I only have to think about putting on my wet suit and I need to take a pee.  But did you know that this might actually be a bit more complicated an issue that you first thought.

Why does you body tell you that you need a pee?  Is it all in the mind or is there something physiological that makes us want to take a leak? Well hopefully this might explain.

Generally the water temperature is colder than the surrounding air temperature, or at least a period of time in the water will have a significant cooling effect as water conducts heat away from the body 20 times faster that air.

So when we are in the water diving, this temperature decrease causes the blood vessels in our extremities, legs, hands, fingers and feet to constrict.  Whilst the skin is more affected by this constriction it can also affect the larger muscles in the arms and legs.

So we end up with a decreased blood supply in he skin andmuscles in those areas but our heart keeps pumping the same volume of blood around the body.  As the vessels in our extremities are constricted this causes and increased amount of blood to go to the organs in the central part of our body, which will generaly be warmer.

Our kidneys produce urine and this is controlled by a hormone called the anti-diuretic hormone.  This hormone regulates when and how much we pee. But due to the increased blood flow to the kidneys as detailed above, the body is fooled into thinking that it has fluid overload and turns off its production of the hormone.  This then makes the kidneys produce more urine to lower the centrally circulating blood volume.

So now we have fooled our bodies into thinking we have produced gallons of fluid, we’ve held it in and it is time to get out of the water and dash to the toilet.  But as we get out of the water the constricted blood vessels now return to normal as does the circulating blood volume. However, the body has taken up fluids to produce urine whilst we were in the water, so the body now thinks he it needs more fluid and draws fluids back from the body.  This makes us feel very thirsty and need a drink.

So we drink tea, water, apple juice and this then gets stored nd makes it worse for the next dive.

So it is not the psychological aspect of looking at rubber and needing to pee but the physiological aspect of our bodies being fooled by the water pressure and temperature that makes it think it needs to pee. 

The worse thing you can do is not drink water before and after a dive.  Dehydration is the one single major contributing factor to Decompression Sickness (according to DAN) so you need to be properly hydrated at al times, especially if diving in a nice warm place.

So take a pee if you need to but make sure you wash your wet suit properly. Firstly after a week on a liveaboard it can get quite smelly but also because urine can rot the neoprene and glues in the suit.

I dive in a dry suit and there are options for taking a pee, especially for us guys.

Option 1 is to use adult nappies for long dives.  Common for techie divers andcatches more than the pee on long decompression stops.  But having tried these I steer away from them (there is a story behind this but I’m not telling here).  This is the only real answer for ladies who dive in a dry suit.

Secondly you can fit a pee-zip in the suit.  This allows for easy access but only when out of the water.  But at least you don’t have to take your whole suit off to take a leak.

Thirdly, and the option I favour, is to use a pee valve.  This is a one valve system that goes through the dry suit and attached via a sticky catheter.  It alows you to take a pee in and out of the water and most have a pressure compensating valve that makes it easy to go at depth.  The only downside is the hassle of “getting attached” which is best done out of sight of your fellow divers.

So I hope this dispels the mystery of that urgent need to pee whilst diving.