Apparatus for facilitating the removal of material deposited at the bottom (6) of a volume of liquid (7) the apparatus including a suction pump assembly (2) associated with a suction head/nozzle (9) mounted to a user handling element (4) and means (24) drivable by the motor for displacing sucked-in water and (8) to a delivery location (11), in such manner that when in use the pump assembly (2) can be submerged, and wherein the suction pump assembly (2) includes means (40) for enabling controlled air escape from the vicinity of the means (24) for displacing air from of the pump assembly the arrangement being such as to prevent air blockage of and material flow through the pump following raising of the latter out of water.
