When the sensation of thirst appears, the body is already dehydrated, and it is not a legend! The human body discharges water throughout the day. A loss of 1% is thirsty, 10% leads to hallucinations, and a loss of 15% leads to death.
The man can not survive more than 2 or 3 days without drinking. On the other hand, he can survive forty days without eating if he drinks regularly and provides very little effort.