How long does it take to dehydrate at sea?

Answer 1

If you do not drink any water at all, of any kind, between 2-4 days, most likely 3. At that point you would die. If you drink seawater, considerably less than that, as seawater is toxic to terrestrial life if ingested in high quantities. If you drank water, you would most likely survive until the water ran out, at which point you would have 3 days before death.

However, this is assuming you are not in the water. If you were in the water, you would die of exhaustion and exposure long before you died of thirst.