Complete acclimatization requires 2-3 weeks. There is no time for acclimatization. And a good reason why you should consider the length of your trip, the amount of sun and heat to which you will be exposing yourself, the amount of water you can carry, the temperature of the water, wind conditions, etc. before jumping into your boat. During the acclimatization period, major changes occur in the thermoregulatory centers of your brain, within your peripheral vessels, and within your heart. Sweating, and therefore cooling, is increased and begins at a lower core temperature while electrolyte loss from both sweat and urine is minimized.
Metabolic efficiency is significantly increased and more usable energy is produced with less heat.
Cardiac output and peripheral vasodilation are increased while the pulse rate is lowered. Essentially your body increases its cooling capacity, produces less heat, and minimizes electrolyte losses as your brain cells become less sensitive to heat. Most people who suffer from heat related problems do not give themselves enough time to acclimatize. Dehydration occurs when a person's fluid output exceeds their intake, leaving them lethargic, irritable, and sick. It is not restricted to a hot environment and can occur in any environmental condition.