Dehydration is one of the most common problems faced by divers which can lead to decompression sickness, fatigue and hypothermia, to name a few. The best way to combat dehydration is for divers to drink as much fluid as they lose. They should also be aware of practices that can cause dehydration such as believing that coffee, beer and soda provide sufficient fluids and thinking that fluid loss through sweat will stop once they get into the water.

Water, water everywhere – but did you get enough? Read on: you could have a serious drinking problem.

When it comes to divers and dehydration, first there’s the bad news and then there’s the really bad news. The bad news: dehydration is thought to be the most common physiological problem among divers. The really bad news: dehydration can also be a significant factor in the onset of decompression sickness (DCS). The explanation is simple. Divers do a lot of dumb things that result in their being dehydrated to some degree. Unfortunately, that condition sets in motion a chain of events that can lead to DCS: dehydration lowers blood volume, causing your body to shunt blood away from skin and muscles and reroute it to vital organs. The end result is less blood flow to assist in the safe off-gassing of nitrogen built up in your tissues.

In addition to DCS, dehydration plays a significant role in fatigue (with less blood volume, your heart has to pump harder and faster), hypothermia (less blood volume and shunting also mean less heat flow), even exhaustion – all three can be dangerous.

Finally some good news: The rule for avoiding dehydration is simple – take in as much fluid as you lose. Easy, right? Well, don’t put the cap on your Evian just yet.

Dumb Things Divers Do To Get Dehydrated

Deliberately not drink before a dive in order to reduce the “P” factor down below.

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Immersion diuresis – that familiar urge to pee while diving – is caused by two factors: (1) increase of blood volume to your body’s core due to water pressure and preferential shunting, stimulating the kidneys to produce urine; and (2) inhibition of the anti-diuretic hormone caused by cool water against your skin and also increased pressure. Notice that the words “proper hydration” did not appear above.

Think they get plenty of fluids on a dive trip by drinking gallons of coffee, tea, soda and beer.

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These diuretics actually cause you to lose more fluids than they provide. If you absolutely must have caffeine and alcohol on a dive vacation, drink extra fluids to compensate for their diuretic effects.

Don’t worry about fluid loss through sweat. Once in the water, they’ll cool off and stop sweating.

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Hot weather can increase fluid loss through sweating up to 14 times the normal amount. Exercise can increase it up to 50 times the normal amount. That means when diving in a tropical environment you could need up to five quarts more fluid per day than normal – just because of sweating.

Think they’ll look like a dweeb sipping on one of those trendy bottles of water all day; besides, the dive boat will provide good fluids.

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Don’t bet on it. The boat is most likely to have caffeine-laden drinks. And the amazing thing about those trendy water bottles with the sip tops? Carry one with you and it’ll be magically empty in a few hours.

Believe the air in a scuba tank is the same as regular air: 79 percent nitrogen, 21 percent oxygen, right?

Wise Up

Yeah, and 100 percent bone-dry. Tank air is so dry, it causes twice the amount of fluid loss through respiration as normal. Air taken into your lungs gets moisturized; most of that moisture is lost when you exhale. And although some regulator devices may keep you from getting scuba dry mouth, none has any significant effect on body fluid lost in this manner.

Are Those Electrolyte Replacement Drinks Better Than Water?

In some ways, yes – especially after a long dive day when you sweat enough to lose a significant amount of Most of these concoctions (see chart) contain sodium and potassium, minerals essential to your body’s ability to absorb fluids. These drinks can also supply carbohydrate energy for your muscles and stimulate your thirst mechanism, causing you to drink more.

What About Salt Pills?

Forget ’em. Best case, they have no effect. Worst case, they can add to your fluid loss via the same mechanism that makes seawater undrinkable. If your body becomes loaded down with excess salt, your kidneys are stimulated to flush it out by drawing water from your overall supply to make more urine. That’s why you die of dehydration faster by drinking seawater than not drinking at all.


Learn to listen to your body: It will let you know if you need more fluid. Common early warning signs of dehydration include:


If you experience these signs, get out of the sun and drink lots and lots of fluids. If they persist, leave the diving for another day.



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