Isn't it an irony that while you are scuba diving you run the risk of dehydration underwater even while you are enveloped by millions of gallons of water?
Ironic but true. Scuba diving can get a scuba diver dehydrated if there is an inadequate quantity of water in his body. That can cause major problems as water is crucial for the smooth functioning of a dozen biophysical systems and biochemical processes. At the cell level, chemical reactions in the cell require water. At the tissue level, water keeps the tissues flexible and plump. Water is also needed for blood production and circulation through the cardiovascular system.
A scuba diver can lose fluids through sweat or urination. Yes, divers do sweat even underwater. But breathing causes the most loss of water for divers. Have you ever observed what happens when you breathe near a piece of glass? The glass becomes foggy. This shows that when you breathe normally, you are expelling high amounts of moisture into the air. Since the scuba tanks contain air that is drier than surface air, you tend to breathe out more moisture underwater. Moisture tends to flow from wet to dry areas just as heat gets transferred from warmer to cooler bodies.
Lowered concentration of fluids in the blood can cause serious consequences. If a diver is dehydrated his muscle tissues will receive reduced blood flow. This affects the ability of his body to absorb and release nitrogen, thereby altering the time required for ascending safely. A diver must ascend at a rate lesser than 30 feet per minute and also make several stops on the way up. If these safety rules are ignored, the diver can suffer from decompression sickness - whose symptoms include cramps, joint pain, and many other serious consequences.
Dehydration affects the rate of nitrogen release. This makes ascents take longer and the diver's oxygen may run out. In this situation, a diver faces an unpleasant choice. Compared to decompression sickness, dehydration causes lesser harm. Yet, the consequences like lowered blood flow, which makes the heart pump faster are still unpleasant enough and you must make all efforts to avoid this. If dehydrated, the diver will fatigue more rapidly, spoil his enjoyment and have to surface quicker.
It is not difficult to achieve the proper level of hydration before and while scuba diving. Before setting off, just drink lots water or a sports drink which does not contain too much sugar. In warmer weather and for longer dives, you will need to drink more fluids. Drink slowly, so your body gets enough time to absorb the fluids without the kidneys getting overwhelmed. But remember to avoid caffeinated drinks like coffee and colas or any alcoholic beverages for many hours before the dive.
Inadequate fluid in the blood vessels of the neck and head cause headaches, so look out for headaches - they are the first indication that you may be facing dehydration. Before the dive, examine your urine to ensure that it's clear and light colored. Once you have surfaced, re-hydrate slowly.
So, use common sense and go for safe dive!