A method of controlling a robot configured to clean a hull of a vessel whilst travelling over said hull, the method comprising: receiving at least one signal indicative of a speed of the vessel; during cleaning being performed by the robot, detecting that cleaning being performed by the robot is to be paused based on (i) determining, from said at least one signal, that the speed of the vessel exceeds a predetermined speed threshold, or (ii) predicting, using said at least one signal, that the speed of the vessel will exceed the predetermined speed threshold within a predetermined time period; in response to said detecting that cleaning being performed by the robot is to be paused, outputting a pause cleaning signal indicating that said cleaning is to be paused; whilst said cleaning is paused, detecting that cleaning performed by the robot is to be restarted based on the determining that the speed of the vessel has dropped below the predetermined threshold, and in response, outputting a restart cleaning signal indicating that cleaning by the robot is to be restarted.