How about snorkeling, scuba diving, fishing........ you're gonna be on a boat! Take advantage of the boat and what it has to offer while you have it. Enjoy!
if it's day time, (hopefully).. maybe you can do tubing, or jet skiing, or if you're looking to do something off of the charter boat, check into all the touristy crap tourists do in your area where ever you are. might jumpstart your thoughts.
im on it..? there will be boys and girls...my parnets will be around so don't say like make-out party and i want nuthing gay like pin the tail on the donkey plzzz answer