The one I rode was loads of fun in terms of going anywhere. I saw a video of the Surly Pugsley riding thru top bar submerged deep water, that thing will float too. The place I test rode it at was an X-Games store in Port Orange, FL, they had a pool, but I wasn't dressed to ride the bike into the pool and tried to float it or see how deep I could ride it ? Maybe with a snorkel or scuba, you could go really deep with it ? Had I been prepared & allowed to, I would have tried the pool out too.

http://vimeo.com/11056499
http://www.youtube.com/watch?v=5rUaWj6Xk70
http://www.youtube.com/watch?v=9hVeI5s75lU