I wasn't sure whether motors requires an ESC or not. Is this so that the correct amount of current is drawn for the motor and battery? If so, could it theoretically be replaced by the correct resistors for this simplified use?
Also, perhaps I should clarify about the radio, I didn't decide not to use it because I thought it would be expensive. One of the constraints of my project was to make the boat autonomous/self-guided. Thanks for the suggestions though, hopefully someone else will have something to suggest for the hull shape and materials.