Marc,
Take a look at fishing kayaks. There are made specifically for fishing and emphasize stability over all else. They come both sit-on-top and cockpit style. I would think that a cockpit and maybe even a waterproof hatch would be a plus for protecting camera equipment. One example is the Heritage FeatherLite Angler. 9.5 feet long and 30 inches wide at 37 pounds. There should be a picture of this at
http://www.outdoorplay.com/store/Product3.0.asp?
DeptID=438&SKU=BRE_HEFA9
Another alternative is to get a Canon digital camera with image stabilization techology and take hand held shots at 1200mm (35mm format equivalent).
Tommy T.