The idea of becoming dehydrated in a sport conducted solely in water is an odd one, and yet it’s something that has probably happened to most divers at some point. Although the percentage of water in our bodies fluctuates, its importance in terms of basic bodily functions is a constant. Our cells require water to conduct important chemical reactions, while our joints need it for lubrication. Cardiovascular efficiency, temperature regulation and the removal of bodily waste also depend on sufficient water in the body. Statistics show that even a 2 percent water loss can drastically affect our physical performance, and as a result the basic recommendation for water intake is 3-4 quarts per day for men, and 2-3 quarts per day for women. As divers, we often require much more water than the norm in order to keep the negative effects of dehydration at bay.
Staying Hydrated When Diving
Several factors put divers at risk of dehydration. First, most dives take place in salt water and in tropical, sunny climates. Spending time at sea results in prolonged exposure to salt water, not only while we’re immersed in it, but also during boat rides to and from shore. Salt is naturally absorbent, and while it coats our bodies it is constantly drawing water from our skin. When the water evaporates, the salt left behind rapidly increases the rate at which our bodies lose moisture.
Hot weather and heightened chances of sun overexposure are other risk factors for dehydration. Hot weather — especially for those unused to it and to increasing their water intake accordingly — leads to profuse sweating, both during gear set up and throughout the dive itself. It’s often hard to tell whether you’re sweating beneath your exposure suit, especially when underwater. Often, divers spend too much time in their exposure suits before getting in the water, leading to overheating and ultimately, severe dehydration.
Too much sun can also result in sunburn, causing the body to flush fluids to the affected area in an attempt to mitigate the damage. These fluids form as sweat on the skin, which quickly evaporates in hot and humid tropical air. Sweating is a constant reality in diving, especially when transporting heavy gear to and from the point of entry. In both hot and cold climates, divers must also consider wind exposure when considering the risk of dehydration. Boat journeys are often windy and seemingly cool, which prevents divers from realizing that they are becoming burnt and exacerbates moisture evaporation from the skin. Boat diving can also trigger seasickness and vomiting, which causes further dehydration due to loss of bodily fluids and electrolytes.
Although topside conditions are certainly a major contributor to the heightened risk of dehydration for divers, two of the most important factors occur underwater. All divers joke about urinating in their wetsuits, but there’s a scientific reason behind our need to pee while diving. The weightlessness of the underwater world combines with increased pressure to trigger a phenomenon known as immersion diuresis. Whereas blood pools in our extremities on land, it concentrates in the body’s core underwater, tricking the body into believing its blood pressure is too high. This causes the body to flush fluids via increased urination as a way of correcting the perceived imbalance. The second cause of dehydration while diving is the dry air in our cylinders. Respiration always results in some water loss, but because compressed air contains almost no humidity, more moisture is drawn from our bodies while diving than normal.
The risks of becoming dehydrated are serious, and symptoms include headaches, a dry mouth, extreme thirst, dizziness, confusion and fatigue. A dehydrated diver’s urine will typically be darker than usual, or will be severely reduced. The production of concentrated urine can lead to the formation of kidney stones, and an increased susceptibility to urinary tract infections. Fatigue results in overexertion and poor air consumption, while the thickening of the blood due to water loss can severely disrupt the circulatory system. Reduced blood flow to the muscles can trigger cramping, high blood pressure, rapid heartbeat and a lack of awareness; most importantly, the blood’s reduced ability to transport gases can increase the risk of decompression sickness. The body may not absorb and release nitrogen as efficiently, putting a diver in danger of breaching safe ascent rates.
As serious as the effects of dehydration can be, it is easily avoided with a series of simple precautions. Drink plenty of water before, during and after diving. Make sure to hydrate on surface intervals, and although water is generally best, sports drinks with high electrolyte levels may be advisable to replace lost body sugars after vomiting. Reduce the risk of vomiting in the first place by taking preventative measures against seasickness — there is no shame in taking medication, but make sure that it’s non-drowsy so it doesn’t impair your ability to function underwater. Seek the shade wherever possible. Surface intervals and long boat rides may seem like the ideal tanning opportunity, but are more likely to result in sunburn and dehydration. When there is no shade, apply sunscreen liberally, and don’t forget to reapply upon surfacing from your dive. (Just make sure it’s a coral-safe product). Rinse off as soon as possible upon returning to shore to remove salt from your skin, and wear wind protection when necessary. Constant fluid replacement is the most effective way to prevent dehydration, but remember that caffeinated drinks, sodas and alcohol are not suitable water alternatives. By following these basic steps, diving can be both fun and safe even on the hottest days.