I have a HUGE Orange Crush acan, taking over a bottom rock in my reef. Eventually, it's gonna be the only coral left in the tank, if I don't find a way to frag it (very aggressive coral).
DC battery operated tools will function under water (like a battery powered dremmel) but I'm not sure what sort of grease or other things they could give off and it would probably be one time use unless you really rinsed and dried everything. That pigpen guy with the 20k gallon tank uses standard power drills when he plants frags.
It is absolutely out of the question to remove this rock. I'd have to tear the entire thing apart to get to this rock. For anyone who has seen my tank, most rocks are held together by the corals themselves & this would completely ruin my tank.