surfing a long boat is a bit different than catching waves with a small craft. Aussies and South Africans have been surfing on skis for decades now and the trick is to paddle fast enough to match the swell and stay on the top of the wave rather than surf it all the way to the bottom. If you just sit there and try to catch the wave like a board/waveski or surf kayak then you will broach even with a rudder. I am only assuming that similar principles will apply to a sea kayak as my experience in the surf is limited to short waveskis and very long ocean racing skis. the tail end of this link shows some ski surfing.
Cheers
http://globalsurfski.se/2009/03/15/epic-v12-surfski/