Odds are the heli would be ruined. If, and it's a big if, you're running absolutely pure water through the hot tub, it'll probably be fine; pure water is a great insulator, so the circuits can't short. On the other hand, the motor probably isn't prepared to put out enough force to displace the water, so it wouldn't be able to fly out, and trying might burn out the motors. Of course, the RC signal probably won't cross the boundary into the water anyway, so it probably won't respond to any command. Should be fine if you leave it to dry though.
In the entirely more likely situation that your water has some level of mineral content, it'll probably short out the board and the motors soon after submergence. That would be A Bad Thing.
In either case, it's not any danger to people in the hot tub. Assuming this is running off of regular consumer level batteries, they aren't capable of putting out anywhere near enough current for you to feel it (unless it's touching you maybe), much less harm you. It would be like licking a D battery.