Hmm, I think perhaps the reason why no-one has responded to you post yet is because it's a very broad question...it's like saying "What kind of car should I get?" It all depends. What level of robotics are you looking to do? Do you just want a remote controlled ship (just something that goes left, right, and forward? You can do that simply with a commercial Radio Controller kit, with a servo and an esc (being wary of waterproofing of course). Are you looking for any autonomy? You'll need at least a simple micro controller. Do you want visualizations (a camera?). Are you taking any sensor readings? Tell us exactly what you want the ship to do.
