Dehydration after diving on Phi Phi: how to stay hydrated between dives
Dehydration after diving is common on Phi Phi: dry tank air, tropical sun, a hot wetsuit and the odd late night all add up. Staying well hydrated makes dive days more comfortable and is part of diving safely, but unusual symptoms after a dive are a different matter and need oxygen and emergency help, not a drip.
The short version
Hydration for divers in five points
- Start hydrated: drink water the evening before and with breakfast, and go easy on alcohol the night before.
- Sip between dives: refill your bottle on the boat and drink during every surface interval.
- Add electrolytes on long, hot days or if you have been seasick.
- Watch your pee: pale yellow is the goal; dark and infrequent means drink more.
- Unusual symptoms after a dive (numbness, joint pain, weakness, breathing trouble) are an emergency: oxygen, your dive centre and 1669.
Why divers dehydrate so easily
Divers lose more fluid than most people realise, and on Phi Phi the conditions make it worse:
- Dry air: the compressed air in a tank has almost no moisture, so every breath underwater dries you out a little.
- Immersion: being in the water shifts blood towards your core, and your body responds by producing more urine. Many divers notice they need to pee after a dive.
- Heat and sun: boat decks in the Andaman Sea are hot, shade can be limited, and you sweat inside a wetsuit before and after each dive.
- Seasickness: vomiting on a choppy ride out to the dive sites quickly drains fluid and salts.
- The night before: Phi Phi is famous for its nightlife. Alcohol makes you pee more and a hangover on a dive boat is a bad combination.
- Coffee and energy drinks: fine in moderation, but they don’t replace water.
Why hydration matters for diving safety
Feeling thirsty and headachy is unpleasant, but dehydration also matters for safety. Dehydration reduces the volume of your blood plasma, and blood carries the nitrogen you absorb during a dive back to your lungs to be breathed out. Divers Alert Network (DAN) Europe runs a whole campaign on this, called “More water, less bubbles”, and its research has linked good hydration before a dive with fewer bubbles circulating afterwards. Dehydration is widely considered one of the risk factors for decompression sickness (DCS).
Hydration is not a substitute for safe dive profiles, sensible ascent rates and safety stops. But it is one of the easiest things you can control.
A Phi Phi dive-day hydration plan
Most Phi Phi dive trips leave from Tonsai pier in the morning and do two or three dives, often with lunch on the boat. Here is a simple plan:
- The evening before: eat a proper dinner, drink water with it and keep alcohol light. Get to bed at a reasonable time.
- Breakfast: a glass or two of water plus breakfast. If you are prone to seasickness, ask the dive centre for advice before you board.
- On the boat: bring a refillable bottle and sip during the trip out and every surface interval. Stay in the shade between dives.
- Hot days or seasickness: mix an electrolyte sachet into your water to replace salts as well as fluid.
- After the last dive: keep drinking through the afternoon. Wait before the first beer, and check your pee is pale before you head out.
You don’t need to force litres of water down at once. Steady sipping across the day works better and is kinder on a stomach that is bobbing around on a boat.
Signs of dehydration after diving
The NHS lists the usual signs of dehydration as feeling thirsty, a headache, feeling dizzy or light-headed, tiredness, a dry mouth and lips, dark strong-smelling pee and peeing less often. These usually improve within an hour or two of drinking fluids with electrolytes and resting in the shade.
The tricky part is that some of these symptoms, such as tiredness, headache and dizziness, can also be early signs of decompression sickness. That is why any symptom that is unusual for you, that gets worse rather than better, or that appears with numbness, tingling, weakness, joint pain, a rash or breathing problems should be treated as a possible dive injury.
Suspected decompression sickness is an emergency, not a drip
Joint or muscle pain, numbness or tingling, weakness, unusual fatigue, dizziness or vertigo, an itchy or blotchy rash, confusion, or shortness of breath within 24 hours of diving can be decompression sickness. Most cases show up between 15 minutes and 12 hours after surfacing. Give 100% oxygen if it is available, tell your dive centre and call 1669 (Thailand emergency medical services). The DAN emergency hotline (+1-919-684-9111) can advise on the next steps. Decompression sickness needs assessment by a doctor and often recompression in a hyperbaric chamber on the mainland. A hotel IV drip is not a treatment for it, so please don’t wait for one.
Can an IV drip help divers?
For ordinary dehydration, yes. If you have been seasick, are run down after several days of back-to-back dives or have mixed diving with a big night out, a drip on a rest day can rehydrate you quickly in your room. Our dive and energy IV drip is designed for exactly that, and the hydration IV drip is a simpler fluids-and-electrolytes option.
There are two important limits. First, an IV drip is never a treatment for suspected decompression sickness: that needs oxygen and emergency medical care. Second, there are no fixed rules on having a drip shortly before or between dives, and the cannula leaves a small puncture in the skin. If you are thinking about a drip on a dive day, ask your dive centre and our nurse first, and tell the nurse about your dive plans. For most divers the simplest option is a drip on a non-diving day.
Other ways to look after yourself on a dive trip
- Use reef-safe sunscreen and cover up between dives; sunburn adds to fluid loss.
- Eat lunch on the boat even if you are not hungry. Food helps you hold on to fluids and salts.
- Plan a non-diving day every few days on longer trips, and avoid diving with a heavy cold or a hangover.
- Follow your dive centre’s advice about the gap between your last dive and your flight home.
Diving FAQ
Diving and dehydration: your questions
Does dehydration cause decompression sickness?
Dehydration is considered a risk factor rather than a direct cause. It reduces blood plasma and may slow how nitrogen is cleared after a dive, and DAN research links good hydration with fewer bubbles.
Is a headache after diving just dehydration?
Often, yes, especially on a hot day. Drink water with electrolytes and rest in the shade. If the headache is severe, gets worse, or comes with numbness, weakness, confusion or breathing problems, treat it as a possible dive injury: oxygen, your dive centre and 1669.
Can I dive with a hangover?
It’s best not to. Alcohol and dehydration raise your risk underwater, affect your judgement and make seasickness worse. Rest, rehydrate and dive the next day.
Can I have an IV drip before diving?
There are no fixed rules, so ask your dive centre and our nurse first. Most divers book a drip on a rest day instead. A drip is never a treatment for suspected decompression sickness.
How much water should divers drink?
There is no exact number. Sip steadily through the day, more in heat or if you have been seasick, and aim for pale yellow pee.
Keep reading
Recovering between dive days
See our dive and energy IV drip on Phi Phi for rest-day recovery, or read IV drip vs drinking water to see when fluids by mouth are enough.
Sources: DAN Europe: Hydration and diving · DAN: Treating decompression sickness · NHS: Dehydration. Last updated October 2026.
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