A system for underwater cleaning, containing an underwater cleaning robot which is designed to be operated below a water surface of a water basin, and a control unit for controlling the underwater cleaning robot, wherein the underwater cleaning robot comprises: a locomotion device for moving the underwater cleaning robot under water, a cleaning device for cleaning an object under water (2, 3), a control device for controlling the locomotion device and/or the cleaning device and a communication device (26, 27) for receiving and/or transmitting signals from outside the underwater cleaning robot, and vice versa, wherein the communication device comprises a first ultrasonic transducer for receiving ultrasonic signals transmitted under water, wherein the communication device is designed to transmit electrical signals corresponding to the received ultrasonic signals to the control device, and wherein the system furthermore comprises a second ultrasonic transducer which is connected to the control unit located outside the water basin and is designed to be located below the water surface in the water basin for converting signals emitted by the control unit into ultrasonic signals and for emitting the ultrasonic signals underwater. a control unit for controlling the underwater cleaning robot, wherein the underwater cleaning robot comprises: a locomotion device for moving the underwater cleaning robot under water, a cleaning device for cleaning an object under water (2, 3), a control device for controlling the locomotion device and/or the cleaning device and a communication device (26, 27) for receiving and/or transmitting signals from outside the underwater cleaning robot, and vice versa, wherein the communication device comprises a first ultrasonic transducer for receiving ultrasonic signals transmitted under water, wherein the communication device is designed to transmit electrical signals corresponding to the received ultrasonic signals to the control device, and wherein the system furthermore comprises a second ultrasonic transducer which is connected to the control unit located outside the water basin and is designed to be located below the water surface in the water basin for converting signals emitted by the control unit into ultrasonic signals and for emitting the ultrasonic signals underwater. a locomotion device for moving the underwater cleaning robot under water, a cleaning device for cleaning an object under water (2, 3), a control device for controlling the locomotion device and/or the cleaning device and a communication device (26, 27) for receiving and/or transmitting signals from outside the underwater cleaning robot, and vice versa, wherein the communication device comprises a first ultrasonic transducer for receiving ultrasonic signals transmitted under water, wherein the communication device is designed to transmit electrical signals corresponding to the received ultrasonic signals to the control device, and wherein the system furthermore comprises a second ultrasonic transducer which is connected to the control unit located outside the water basin and is designed to be located below the water surface in the water basin for converting signals emitted by the control unit into ultrasonic signals and for emitting the ultrasonic signals underwater.