if the doors strong enough, you could back the boat upto the jetty, which has a recess to accept it so it is flat to the jetty, inside the boat you could have a moving ballast weight where as it moves towards the ramp it provides the force necessary grip to the dock, plus as the model truck fraternity has in one of the youtube vids a pair of pins that locate into the ramp painted as traffic cones they would not look out of place, doesnt matter if the loco over runs - the ramps on the jetty, plus as in most rail sets the last piece of track is isolated temporarily, if the loco is long enough the rear wheels are still on the isolated track and the front on the boat, when it comes time to reverse the train, the isolated track is set for reverse and the train reverses. decoupling could be on the boat with a plate between the tracks and lifted with a servo.