Lenses for consumer digi-cams?

I am very happy with my Canon SD 870 and underwater case and wondering whether to take it a step further and get a wide angle lens. An mount base and wide angle lens would cost almost as much as the underwater case and the camera together. I am not sure if it's worth it for now...

I also not sure about whether I should get a fish-eye lens or a 28mm wide angle lens (which has the advantage of working above water too).

I appreciate any comments,

Well, I am a macro maniac, so a tray with an external strobe would do it for me.

I have seen some nice wide angle photos though....if you can color correct and it is a far away shot you can eliminate strobes which aren't effective far from the subject or for many wide angle shots.

A 28mm surface lens produces a 35mm underwater shot! The good thing about most wide angle lens is the fact that the depth of field is so great! Most wide angle lens used for underwater work have a tremendous focal range some as great as 8" to infinity! It is the single most improvement for most beginners through intermediate you cam make next to good lighting! You can still get close with the wide angle, it can produce great results:D

Here is an example of close yet the face and the tail are in focus. Something not done with most macros. It was shot with a 10mm to 22mm zoom.
http://www.scubamagazine.net/photo/d..._C_A_II_07.jpg

Thanks for the answers! I get from them that I may be better off first investing in lighting and then in lenses. Any recommendations?

Inon and Ikalite both make great strobes for your camera.