Abstract: A remotely operated submersible vehicle (21), wherein the vehicle includes flotation cells (62) to provide positive buoyancy, and the vehicle is connected to a disposable clump weight (22) of sufficient weight to overcome the positive buoyancy. The connection between the clump weight and the vehicle is by way of a cable (25) which can be wound onto and off from a drum winch (45) within the vehicle to control its height off the seabed (23). The trim of the vehicle is maintained by adjusting the horizontal position of a cable guide (43) through which the clump weight cable (22) passes, the cable guide (43) being moved longitudinally and transversed by hydraulic cylinders (47). Control signals to control and monitor the operation vehicle are provided via an umbilical cable (29) extending from a ship (76) or platform on the surface.