I have done a bit of photography from a my Kayak. I have a Tui by Q-kayak.
http://www.q-kayaks.co.nz/asp/kayaks.asp?ID=tui . It is a single person touring kayak.
I have not used a fishing kayak, however I suspect these would be idea for photography being more stable and more room for equipment.
The Hobie kayaks have a foot peddle system fishing kayak which would allow you to move leaving your hands free to used the camera. I find it annoying having to juggle the paddle and camera. When there is a breeze sometimes you need to keep reaching for the paddle to keep position and direction for the shot. Also most of the water spary come from my paddle, so when you grab the paddle you run the risk if you dont put the camera in the water proof bag. I use soft waterproof bag which is specifically made for kayaking/boating. these are the type you put your gear in and roll down the top of the bag and then clip each end together.
Some of my observations/ideas.
1. Room is limited. I take one camera with one lens and have to keep it between my legs. The access hatches are generally not accessible from inside the kayak. (touring/sea style)
2. Get a rudder. Some kayaks dont have them and others have them as optional extras.
3. Get drip guards on your paddle.
4. Be aware of the weight of the kayak. Some can be very heavy.