Take on boats: death on contact with submerged vehicle
... apparently you can't
After so awesomely landing the preview chopper in the middle of a pond, I tried to see what quirkiness would ensue. Impressively it stayed afloat for awhile unharmed until I switched the battery back on and the engine went critical. then exited the vehicle and the blades magically disappeared.
Anyways the important point was that on exiting the vehicle then returning sometime later and swimming up against it, it resulted in an insta-death.
so much for taking on boats.