the only way I can think of to achieve something like this is to have flat ground under the water and move the wheels on those vehicles to be lower
I do think there may be some weird physics since they will be driving in water
if you make the water have collision, then the boat addons will work, but the rowboats will not and players will be able to walk on water
you could try enabling raycasting, but I think vehicles can go through bricks that have collision or raycasting off, so the lack of collision will break it