An underwater cleaning device comprises a disc member (100； 110； 120； 130； 140； 150) rotatably connected to a mounting member (101) and having a first disc side (104a) arranged to face a submerged object to be cleaned. The disc member comprises a plurality of nozzles (105) fluidly connected to conduits (106) configured for supply of pressurized liquid, arranged on the first disc side (104a) and configured for discharging pressurized liquid tangentially with respect to the disc member and away from the disc first side (104a)； causing a disc rotation (R). At least one through-going opening (103； 107； 122) is arranged between the disc first side (104a) and an opposite disc second side (104b), and a plurality of blade members (111； 121； 131) are arranged radially on the disc first side (104a). The openings may be one or more circumferential slits and/or a circumferential row of holes arranged concentrically on the disc member. An underwater cleaning apparatus (1) one or more disc members (100； 110； 120； 130； 140； 150). The cleaning apparatus is useful for cleaning a seine or net in a net pen.An underwater cleaning device comprises a disc member (100； 110； 120； 130； 140； 150) rotatably connected to a mounting member (101) and having a first disc side (104a) arranged to face a submerged object to be cleaned. The disc member comprises a plurality of nozzles (105) fluidly connected to conduits (106) configured for supply of pressurized liquid, arranged on the first disc side (104a) and configured for discharging pressurized liquid tangentially with respect to the disc member and away from the disc first side (104a)； causing a disc rotation (R). At least one through-going opening (103； 107； 122) is arranged between the disc first side (104a) and an opposite disc second side (104b), and a plurality of blade members (111； 121； 131) are arranged radially on the disc second side (104b). The openings may be one or more circumferential slits and/or a circumferential row of holes a
