Taking LO to the pool for the first time on Sunday. Am I supposed to get a package of those swim diapers? Or the cover that goes over a regular diaper? He's 13 months.

Bonus question - where can I buy them and how much should I expect to spend? No time for online shopping so I need to pick this up at Target, Wal-mart, Carter's, Babies R Us, etc.

THANKS!