If you're wanting a DSLR, I'll second the Rebel Xti... I got one last summer and have enjoyed using it immensely. It always goes with me on hikes and any other outdoor excursion but you won't find it with me on the stream. I believe you can buy a waterproof housing for it if you really wanted to take it with you on the stream but it is quite expensive.
If you're just wanting a good fishing camera to document your catch, I've been using a Pentax Optio W30 for awhile and it has worked great...