Stay wet, BUT.. make sure you have SPF on your lips in the water!
BRING Blistex or something with at least a SPF of 15, or higher.

It was so hot in June when i was there, i ended up with blisters on my bottom lip from staying in the water so much.

Also, i have a bucket hat that i wear on my head in the heat... i wet it at night, and stick it in the freezer.
That hat keeps me nice and cool for some time.