AbstractWhen a remotely operated vehicle (ROV) is lowered from its support vessel by a cable, it rotates horizontally because of external forces as it nears the surface of the ocean. This causes the cable to twist. This paper describes experiments using a model of the ROV ABISMO in a water tank to improve safety by examining the waves and the wake flow of propellers as possible causes of the external twisting forces. These experiments on wave effects evaluated the effect of wave height, wavelength, and submerged depth of the model. In addition, the model was varied to include different configurations of fins and outer covers. The experiments on the effect of propeller wake flow evaluated the effect of the horizontal propeller offset and the submerged model depth. The horizontal rotation of the ROV induced by the waves and the wake flow was observed in some cases. The results showed that the wave characteristics, offset, and submerged depth all influenced the generation of horizontal rotation. It was also found that the addition of a horizontal fin and extended vertical fins reduced the horizontal rotation.