Gil- I got some nice underwater shots via a Fuji Disposable. No fears it will get wet or damaged. They do make an underwater housing for your camera.

The long lens you are looking at is okay - I'd suggest as Masaki said in sticking to the Canon lenses. I find that I shoot either pretty wide or pretty long. Weight for travel is an issue too. That being said, I also like a fast lens. My walk around is now the 24-70L 2.8. The long lens you are looking at is not that fast (smaller number apeture) so it won't work well in low light situations. I have the Canon kit Lens 18-55 for digital that came with the D20 Frank has - we'd be interested in selling, never used.

There are ssome good lens discussions on the forums at www.dpreview.com