Abstract: A fluid jet system for underwater maintenance of a ship hull is provided. The fluid jet system includes an open frame cart having a high pressure fluid nozzle manifold for cleaning and smoothing the submerged hull of the ship. One or more thruster assemblies are provided on the cart for deploying the cart through the water, advancing the cart along the hull and maintaining the cart in contact with the hull. Control of the thruster assembly and fluid flow manifold can be effected from either longitudinal end of the cart. Flexible fluid flow lines interconnect the cart to one or more remote sources of pressurized fluid so that the cart is independently operable. A system for deploying the cart is further provided and includes the necessary high pressure pumps, devices for hose deployment and retrieval, and diver supplies.