Water, water everywhere….as the old saying goes. One of the great paradoxes in diving is that while we are immersed in water we are constantly in danger of dehydration. The consequences of dehydration in diving can be quite severe. For that reason, it is important as divers that we understand the factors that contribute to and thus avoid the complications caused by dehydration.

Dehydration lowers the blood volume in your body. When a diver has less blood volume there is reduced blood flow to the tissues which in turn compromises the body’s ability to wash out or effectively off gas nitrogen. With more nitrogen remaining then in a well hydrated diver, you are at a greater risk of DCS.

Dehydration occurs when fluid intake is not adequate enough to replace the amount of fluid lost. Anything that reduces fluid intake or fluid loss, will increase the likelihood of dehydration. The five ways the body loses fluid is through the lungs, the skin, urination, blood loss and the gut.

During diving, all of the above mentioned methods of fluid loss will occur. Through breathing the super dry air from a SCUBA cylinder, from skin perspiration due to heat and sun or even during cooler weather the heat generated from a wetsuit or drysuit can cause substantial fluid loss. In addition, immersion dieresis or the urge to pee while diving is basically caused by the water pressure on the body tricking it into thinking your bladder is full.

Menstruation has not been shown to have a direct causal effect on DCS, however some women can become slightly dehydrated during their menses.

Many divers travel to tropical destinations and are exposed to a variety of sources of bacteria that can cause diarrhea. Diarrhea is a potentially huge source of fluid loss.

When any or many of these causes of dehydration occur, divers can re-hydrate by drinking plenty of the appropriate fluids. Unfortunately, these fluids are not always readily available. Most dive boats have a limited supply of water on board but often there is not always enough for everyone to adequately supply their needs. I have seen on more than one occasion the water container get spilled and then there ends up being no water!

Soda, coffee, orange juice and many other popular drinks actually contain caffeine a known diuretic. Instead of re-hydrating yourself drinking these products, you may actually further dehydrate yourself. When keeping yourself hydrated, nothing works better than drinking plain old water. Drink a minimum of two liters of water, spread it out over the day rather than in a short period. Drink more if it is very hot out or if you a diving more than a couple of dives in a day.