BTW: Most of these thrusters have a switch to turn them off in addition to the switches to activate them in either direction. Some folks would recommend turning the switch off when you're not using the thruster. I don't but I probably should.
You are correct. When not using the boat the thruster Main Power Battery Switch needs to be in the off position. If your installation does not have one, install one.
Think about your diver under your boat cleaning the thruster fins? ???????