Hi Reak!
The water parks at Walt Disney World Resort are fabulous! My sons and I love them. We actually planned a summer trip to Walt Disney World last year for the sole purpose of visiting the water parks and spending a couple of days in each; the idea was not to visit any theme parks -- that sort of worked until my youngest son, who was 4 at the time, asked when we were going to visit the Magic Kingdom!
In my opinion, Typhoon Lagoon is better for families with very young kids or for older families who want to relax; Blizzard Beach is for teenagers and more active families! However, you can not go wrong with either, and I'm sure there are moms and dads on this panel who would disagree about which is better for younger kids, etc.
With regards to beaches, from Walt Disney World you can reach Cocoa Beach just south of the NASA Kennedy Space Center in a little bit over an hour. There is also
Disney's Vero Beach Resort on the Atlantic Coast; it's a little over two hours away by car. On the gulf side, you can get to nice beaches in about an hour and a half.