I have a nikon DSLR that I take fishing with regularity. I find that it is the only way to really get great pictures whether of fish or landscapes. I have a canon digital point and shoot that takes great pictures that I always keep in the boat for grip and grins.
If you are thinking along the lines of a DSLR, I would personally choose a Nikon. That is personal preference and the debate between Nikon and Canon is much like Chevy vs Ford. They are both great products, I just found the Nikon more comfortable in my hands as the Canons were a little bit small.