have you checked out the Sea Island Sport

http://www.clcboats.com/shop/boats/kayak-kits/fishing-kayaks/sea-island-sport-sit-on-top-kayak-kit.html

Every now and then there's a thread about mounting a seat on top of a  paddleboard, but I haven't seen one about recessing the deck to form a cockpit.

If you put in a cockpit then you have to provide some type of drainage (otherwise you might as well just cut open the cockpit on a standard kayak). For the drainage to work the bottom of the cockpit has to be above the waterline when the boat is fully loaded. So if you're going to recess the deck you'll have to add extra flotation to raise the cockpit floor. That would require changing the hull shape.

The paddleboards have enough stability to allow someone to stand up, as is. If you were to just mount a seat and some dry bags you'd have a place for you and your gear that wouldn't get swamped and you wouldn't have to worry about structural and hydrodynamic modifications.

If you actually want a self-draining cockpit, you'd be much better off doing as Josh suggests and going with the Sea Island Sport. The only thing to keep in mind with that is that there's an absolute weight limit. If paddler, gear and fish exceed that limit the cockpit will go beneath the water line and not drain anymore. The boat won't sink, but there'll be water sloshing around the bottom of the cockpit.

Another good choice for fishing is the Wood Duck series. They have a large cockpit opening for easy entrance and exit, great cargo capacity and are very stable. They are not self draining but if you put in a large dry bag or two in the bow compartment they can't take on much water and will bail quickly.

I have a WD12 and I've had it out in a small craft advisory with 3 foot choppy waves and whitecaps and a 28 mph wind that was blowing against the tide. As it came off one wave the bow would go underwater into the next wave, right up to the coaming, and pop out to the surface. I never felt in any danger, the boat stayed upright and I only took on a few cupfuls of water (I did have a sprayskirt).

Hope this helps,

Laszlo

PS - I also had a catfish tow me in my WD12 down the Patuxent River. That should give an idea of how easy it is to paddle that hull shape.

I like the Sea Island Sport, problem is bait, tackle, anchor, gear and me will crush the weight limit. It needs to be three feet longer with carrying capacity of at least 400 - 450 lbs. I like to fish the ocean, I need a battlewagon.

With a weight requirement like that you might want to look at something like a PM dinghy, Skerry or  NE'r dory. They can't  any harder to stand in than a paddle board and you get seats.

The Expedition Wherry might also be a possibity.