If immersed it in a denser fluid, such as mineral oil or water, it might be very possible. The rotors could be run at lower RPM (possibly with the stock gearbox attached) and the buoyant force would reduce the amount of lift that the rotors would need to provide. It might help to contain the motor(s) in a diving bell an run chain drives to the rotors. The greatest issue might be finding a suitable fluid and a vessel in which to contain it.
I'm not crazy, I just like to think
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