As far as I know there are no plans available. This question has popped up here and there without much success. Do a search on this forum to find the threads. There is a user group for seaquest with a least one member trying to work out a set of plans but I don't have that info on this computer. I think it's on Yahoo but thats just a guess. If your looking for a static model they can be found here and there. Unfortunately the static model is pretty bad as far as the fit up of some of the hull parts. If it's for R/C the trick is going to be propulsion and control, more so on the control end. You may find some pictures posted in past threads showing a very large model of the Seaquest built by a guy in France I think, If not I can send them to you.
Let me know how you make out.
Put your heart into it, well done is better than well said... Ben Franklin