I've been there twice, it's a total riot and i do agree about Chessington and Alton Towers, as much as i enjoy thrillathons, Chessington only does that one thing and Thorpe only does that and wet rides. Alton has a large variety of stuff and if i lived closer to it i'd use that as my choice for when i go to theme parks.
Both times i went i went to the waterpark hotel and it's probably the nicest place as well as having one of the more entertaining water parks i've been to. You can get prescription swimming goggles as far as i know, i'd take a look into it if you'd like to make full use of the swimming area but then i have the same problem and i haven't bothered so it's all down to how much it bothers you i suppose