Lasers need water.
On hot days Lasers need to drink water. It helps to hydrate before going out. The April 2010 Journal of Athletic Training reported that a 2% dehydration before running gave slower times and recommenced 16 ounces of fluid 1 to 2 hours before and another 4 to 8 ounces 15 to 30 minutes before running.
In 2008 the Medical Society in Sports and Exercise found that cyclists that drank cold beverages before and during work out were able to ride longer.
No reason it should not carry over to the active sailor. So if it is hot, start hydration early and if you can, make it cold. .