Lens choice for snorkling/tubing?

I am buying the Canon digital rebel XT, and right now plan to get a sigma 18-200mm f3.5-6.3 and the canon 50mm f1.8. Getting it for a west caribbean cruise.

I am new to SLR's, and starting with the above (tho I am tempted to get the 100mm Macro as well). My question is, which would be good to use while snorkling? I won't be diving much at all with a broke foot, just floating on the top mostly. So I won't be able to get terribly close to most subjects.

Which of the two lenses would be best (or the macro).

Yes, I am looking at the EWA "zip lock baggy", but again it is just for 2-4 feet down, and we are looking at doing a tubing through caves thing, where I don't trust myself not to drop/splash the camera. At this point, especially with the bum foot, there is just no way I am paying another 1-2k for a housing. Our next Hawaii trip, sure maybe then, but for now I need something to snorkle with.

Thanks!

A lens at the 18mm end would be good for that kind of shooting. Just make sure you have one that will fit inside the baggy.

I would also HIGHLY recommend a magic filter for these kinds of photos.

Cheers

James

"I would also HIGHLY recommend a magic filter for these kinds of photos."

You lost me there? Can you point me someplace where I can learn more about a magic filter? Is the pixie dust free or an added charge?

Thanks for the super fast response!

Here's the website: http://www.magic-filters.com/ It's a filter for use with available light shallow-water photography.

Cheers

James