Abstract: A cleaner for a submerged surface (11) comprises a body (15) defining a suction passage (16) and pressure passage (17) therethrough. Suction passage (16) extends between inlet (18) and outlet (19) in the body and is connectable to the inlet of a filtration system by flexible hose (13). Pressure passage (17) extends between inlet (20) and outlet (21). Inlet (20) is connectable to an outlet of the system. Drive means in the form of a water turbine (22) is located in passage (17). Water flow under pressure through passage (17) drives turbine (22) which in turn drives hind wheels (23) to displace the apparatus over surface (11), while debris or the like is sucked up through the suction passage (16).