Combining biking and paddling is cool. But you may find inflatable kayaks a bit lacking for sea kayaking. This thread in Touring shows some ways of transporting a full scale sea kayak with a bike:
http://www.bikeforums.net/showthread.php?t=339849
There are also "foldable" kayaks which pack into a couple of largish bags for transport. This is actually the traditional way of building a kayak, with a rigid frame structure that can be taken apart, and a skin that is tightened over the frame. Their assembly takes a bit longer than pumping up an inflatable kayak, but they are much better at sea. They're also expensive
. One of the best known manufacturers for these is Klepper in Germany (
http://www.klepper.de).
--J