I did this same search last season and found a Kayak I can sit on and use like a bicycle. I had a hard time getting in and out of a regular kayak. So with one you sit on top off its easier to enter from the dock or beach. I find it very enjoyable to use and great exercise. The drawbacks is it can be a little wet on the rough days so wearing a bathing suit is best. Another nice thing, that I didn't take advantage of is that they come in tandem models. So check them out over at Fay's.
http://www.hobiecat.com/kayaking/index.html