Dehydration and Diving: Facts and Myths

While dehydration increases the risk of DCS, just how and when divers should hydrate is still unresolved. Currently, medical experts stress pre-dive hydration but don't comment much on post-dive hydration. Some scientific papers encourage mild to moderate dehydration prior to diving, saying it helps prevent decompression sickness, while others warn against it. Some dive experts counsel against drinking coffee or other caffeinated drinks, but there is some scientific evidence to the contrary. Claudia Roussos, M.D., an anesthesiologist from Boynton Beach, FL, wrote about hydration and diving for the rebreather-focused blog Add Helium ( www.addhelium.com ) so that divers could make smarter decisions about how and when to hydrate during their dive day. Here are some important points:

Urine Color. Several studies have suggested using urine color as an indicator for hydration. Pale yellow urine suggests proper hydration, while brownish urine suggests dehydration, with variations along the color scale. While color is not entirely accurate, you can use it to gauge your own level of hydration.

When to Hydrate. Current studies on hydration and diving are contradictory. Ingesting copious amounts of water pre-dive does not appear to be beneficial because it does not correct dehydration in time. Instead, consuming adequate amounts of liquids (other than alcohol) throughout the entire day is recommended.

What Beverages to Drink. Although coffee and other caffeine-containing beverages may exert a mild diuretic effect, they do not appear to cause dehydration. A more recent study of black tea consumers found no difference in hydration compared to water. It appears that people acclimated to drinking caffeinated beverages are resistant to the diuretic effects, but individuals who abstain from caffeine will urinate more once ingesting it.

You can have your coffee, tea or soda while diving, but go light on the booze the night before, and keep an eye on your urine color.