Then I moved to freshwater trials. I filled a bucket with water and placed it in the bathtub. The battery was re-installed (again, never use a mains-powered device in a wet place!!!), and the motor started with the propeller underwater. Water "boiled" satisfactorily. Power needed rose greatly, to 82 W (8,8 A @ 9,8 V). Perceived thrust was satisfactory, too. So, I judged the propulsion system, as it was, satisfactory for the application, dismantled the test rig, and carefully mothballed all test gear.