Upload & Sell: Off
I have and recommend the Hobie Outback kayak. It's expensive though (around $1800-1900).
It's very stable (I have never felt like it might roll) and has the foot driven Mirage drive and a rudder, so you keep your hand free for your camera. At 12' long it fits nicely in my 8' truck bed, just sticking out past the tailgate a foot or so and is managable for 1 person tno load and unload. I usually go out with my 7D and EF-70-200 2.8 (over my 400 5.6), since you can often get pretty close to birds, gators, and other critters. I usually have an extender if I want more range, but seldom use it. A 600mm lens might be tough to handle though.
I used a fishfinder mount to install a water resistant box to place the camera and lens in when launching, landing, performing maneuvers, or just to rest my arms. If interested, I can send photos of this setup.