Abstract: An explosion proof submersible gearmotor in which a gear reducer has a housing with a sealed chamber and input and output shafts with a gear train connecting the input and output shafts, and in which a sealed motor is mounted on the gear reducer housing and a wall of the gear reducer forms one end wall of the motor, the shaft of the motor being directly connected to the input shaft of the gear reducer. The chamber in the gear reducer contains a non-conducting lubricant, and a moisture-sensing probe extends in the lubricant in the chamber for sensing the presence of water and transmitting a signal in response thereto, indicating a failure in one or more seals of the gear reducer. The operation of the motor of the gear reducer is then either automatically or manually interrupted until the unit has been serviced and repaired.