As a diver, traveler to tropical areas and not used to such warm temperatures, you can easily dry out. And dehydration not only causes headaches, but also increases the risk of decompression sickness. And so the advice is to drink at least 3 liters of water per day and by that we mean real water. Coffee, tea, soft drinks and alcohol dehydrate you, so you continuously replenish your shortages. Do you really drink 3 liters a day but do you have a slight headache? Then it might be wise to take some rehydration salts. Ultimately, you need water and minerals to retain fluids in your body. However, be careful not to drink water with these salts all day long, this will make you over-hydrated and that in combination with diving can cause edema. But a bag of salt a day is fine and prevents many problems,