Dr. Duncan recommends peeing after sex on the beach (or sex anytime, really). This can prevent urinary tract infections by flushing away any bacteria that's gotten near the opening of the urethra. Also take a shower ASAP and rinse your vulva with water to remove sand from the folds there. Sure, the ocean is, like, right there — but if the sand has caused any microabrasions, the salt water may sting. Rinse your butt, too, Dr. Duncan says, to remove any sand that may have crept between your cheeks.