Short answer: divers dehydrate faster than almost anyone else on a summer beach, because the air from a scuba tank is bone dry, immersion itself makes your body produce urine, and a wetsuit on a hot Mediterranean deck turns you into a portable sauna between dives. Drink water steadily from the evening before, keep drinking between the two dives, skip the alcohol the night before, and you remove the most common cause of cramps, headaches and end-of-day exhaustion in one move.
Why Diving Dries You Out So Efficiently
The air you breathe has no moisture in it
Compressed air is filtered and dried before it goes into a cylinder — moisture inside a tank would be a problem. Every breath you take underwater therefore arrives completely dry, and your body has to humidify it on the way in. Over two dives that is a surprising amount of water lost through breathing alone, and you never notice it happening.
Being in the water makes you produce urine
When you are immersed, water pressure pushes blood from your limbs towards your chest. Your body reads that as "too much fluid" and the kidneys respond by producing more urine. It is why almost every diver needs the toilet after a dive and why the effect has its own name: immersion diuresis. It happens whether the sea is 17 °C in winter or 28–29 °C in late summer.
The deck, the sun and the wetsuit
Between dives you are on an open boat on the Antalya coast, often in a wetsuit that is only half peeled off. The sea breeze evaporates sweat before you feel it, salt dries on your skin, and there is no obvious signal that you are losing fluid. A full-day trip runs six to eight hours, so the surface interval is a long time to spend warm.
Last night's drinks
Alcohol is a diuretic, and its effect is still with you the next morning long after you feel fine. A heavy night before a dive day is the single most avoidable mistake we see. Strong coffee on an empty stomach adds a little to the same effect.
Why It Matters More for Divers Than for Sunbathers
Dehydration is not just about feeling thirsty. It thickens the blood a little and reduces circulation efficiency, and poor hydration is widely recognised in diving medicine as one of the risk factors for decompression sickness. It also makes ear equalisation harder because mucous membranes dry out, so a dive that should have been comfortable becomes a struggle — see our guide to equalising your ears. Add muscle cramps in fins and the tiredness that lands halfway through the second dive, and the case for a water bottle becomes very easy to make.
What to Drink, and When
- The night before: water with dinner and no alcohol. This one change does more than everything else on this list combined.
- Breakfast: a proper glass or two of water alongside your tea or coffee, not instead of it.
- Before pickup: another glass. Morning hotel transfer is included on every trip and the exact time is confirmed the evening before, so you will know how much time you have.
- On the boat: keep sipping through the surface interval rather than drinking a litre in one go. Lunch is served fresh on board, which helps replace salts as well.
- If you sweat heavily: a drink with electrolytes or a pinch of salt in food is more useful than plain water alone.
- Skip: alcohol before diving, sugary energy drinks, and endless coffee on the boat.
Signs to Watch For
Dark urine, a headache that arrives with the afternoon, calf or foot cramps while finning, unusual fatigue after the second dive, and a dry mouth that a single mouthful does not fix. If you get a cramp underwater, signal your instructor, stretch the leg and pull the fin tip towards you — with 3–4 divers per instructor there is always someone right beside you to help. Never try to sort it out alone at depth.
Heat on Deck: Small Habits That Work
Peel the wetsuit down to your waist between dives rather than sitting in it fully zipped. Find shade during the surface interval. Wear a hat and drink before you feel thirsty, because thirst is a late signal. Remember that you should not fly within 24 hours of diving, so plan the rest of the day gently — more on that in why you cannot fly after diving.
If you take medication or have a health condition, mention it on the standard diving medical questionnaire we complete before the dive; some medicines affect fluid balance or heat tolerance. We are not doctors and we never diagnose — anything flagged needs a doctor's sign-off, as explained in diving with medical conditions.
Come Prepared, Dive Comfortably
Our full-day boat trips run from €43 to €50 and include two guided dives, all equipment, free two-way hotel transfer, fresh lunch on board and insurance. Pack light and sensibly with the what to bring checklist, browse the dive trips, or message us about anything at all. Reserve free online, pay on the day, cancel free up to 24 hours before.
