HI!
Ray's Splash Planet has a pool and water park:
Park and Rec Ray's Splash Planet (http://www.charmeck.org/Departments/Park+and+Rec/Aquatics/Rays+Splash+Planet/Home.htm - broken link)
Also, Mecklenburg Aquatic Center (MAC) has free swim, swim lessons, and some pretty fun slides:
Aquatic Center Information (http://www.charmeck.org/Departments/Park+and+Rec/Aquatics/Aquatic+Center+Information.htm - broken link)
Hope these help! Happy Swimming!