You're Surrounded by Water—So Why Do Divers Get Dehydrated?
Paul Lenharr Jul 12, 2026
You're Surrounded by Water—So Why Do Divers Get Dehydrated?
When most people picture dehydration, they imagine hiking in the desert or exercising in extreme heat. Scuba diving doesn't usually come to mind. After all, you're surrounded by water all day.
Ironically, divers are especially susceptible to dehydration.
Every Breath Costs You Water
The air in your scuba cylinder is extremely dry. During the compression process, moisture is removed to protect the compressor, cylinders, and regulators from corrosion and contamination.
That means every breath you take underwater has to be humidified by your body before it reaches your lungs.
Over the course of an hour-long dive, that moisture loss adds up.
Now combine that with:
- Hours spent in the sun between dives
- Wind exposure on the boat
- Wetsuits and drysuits that trap heat
- Multiple dives in a single day
It's easy to understand why many divers finish the day dehydrated without ever feeling particularly thirsty.
Don't Forget Immersion Diuresis
Have you ever noticed you need to urinate shortly after entering the water?
That's not just coincidence.
Immersion causes blood to shift toward your chest. Your body interprets this as having excess fluid and responds by increasing urine production—a normal physiological response called immersion diuresis.
It's another reason divers lose fluids throughout the day.
Why Hydration Matters
Maintaining hydration supports normal circulation, temperature regulation, and overall comfort while diving.
Although no beverage can prevent decompression sickness, dehydration is considered one of several modifiable risk factors associated with DCS. That's why organizations like DAN encourage divers to begin dives well hydrated as part of an overall conservative approach to dive safety.
Why Electrolytes Are Part of the Picture
Water replaces fluids, but electrolytes help maintain normal fluid balance and support muscle and nerve function.
For long dive days, hot weather, or tropical vacations, many divers find that including electrolytes in their hydration plan helps them stay ahead of fluid losses.
That's one reason Southern Maryland Divers is proud to carry LMNT—a sugar-free electrolyte drink mix designed to replenish sodium, potassium, and magnesium without unnecessary additives.
Practical Dive-Day Hydration Tips
✔ Start hydrating the evening before long dive days.
✔ Drink fluids consistently rather than all at once.
✔ Include electrolytes when spending long hours in the heat or making multiple dives.
✔ Limit alcohol before and during dive days.
✔ Continue rehydrating after your final dive.
Final Thoughts
Hydration begins long before you step onto the boat.
Building good hydration habits is one more way to prepare your body for a full day underwater and enjoy every dive to the fullest.
If you're curious about LMNT or want help choosing a flavor, stop by Southern Maryland Divers before your next adventure. We'd be happy to help.