15mm fisheye on a crop camera

A bit of advice please!

Later this year, I'm off to the maldives, and there is a manta cleaning station nearby. With my current gear, I've got 2 lens options, and wondered what experience others have with the lenses. The first is as the title suggests, using a 15mm fisheye with a cropped sensor, the other is using a canon 10-22mm. Unfortunatly, I doubt I'll be able to stretch to the required port extensions and gears as well as buying the tokina 10-17

cheers

Mike

I shoot with the 15mm FE on a canon 20D. I quite like it, but am often doubting if I should swap with a 10-17mm (which was not there yet when I bought the lens). I would probably choose either the 10-17 or the 15 FE. I have a 10-22mm, but not yet used it under water (there are some threads over here regarding corner sharpness etc)