We are getting a pool put in and we have thought the same thing too. I have heard good and bad about the chlorine, etc. So, I think we are just planning on having a kiddie pool w/ just plain water in it for Mojo. Although, I might put him on the raft with me from time to time.
Here's the link to my post about it awhile back...maybe you can find some helpful info there......
http://www.yorkietalk.com/forums/showthread.php?t=78343