What to do in Myrtle Beach w/ 9 mo. old?

Hi everyone!! We live in NC and are going to be visiting the SC Myrtle Beach area next week. Can any of you suggest some things to do, places to visit with our DS? Preferably free or cheap! I would love to take him to some museums, but I don't know what they have there.

Any input is welcome!!! Thanks Mamas!!