There are a lot of reasons people go on spring break, and there are a lot of reasons most people don't share those reasons with their parents.
I'm not saying you can't have a good time with your friends (the number one excuse among people who want to appear innocent), but there's a chance that "good time" is going to involve certain extracurricular activities.
Based on every single movie I've seen, if a girl asks you to rub sunscreen on her back in Panama City Beach in the month of March, it's your duty to say "yes" and eventually have a passionate moment that leaves you emotionally torn.
However, in those movies the girl doesn't usually have a penis. This one does.