Abstract: This disclosure relates to an underwater excavation apparatus comprising a tube in which a propeller is mounted for rotation. The tips of the propeller blades are formed with jets supplied from a high-pressure water supply through passages in the propeller blades. The jets impinge on vanes mounted on the tube wall around the propeller to cause the propeller to rotate and thereby draw water through the tube from a inlet at one end to an outlet at the other end to act on the seabed. The apparatus is particularly useful for excavating trenches on the seabed and exposing previously covered installations on the seabed.

Abstract: A pump casing made of sheet metal has an outer casing having a suction nozzle, and an inner casing housed in said outer casing and spaced therefrom. A resilient seal is disposed in a gap defined between the outer casing and an inner casing. An impeller is rotatably disposed in the inner casing with a clearance defined between a liner portion of the inner casing and the impeller. The resilient seal is effective to absorb deformations of the outer casing, such deformations of the outer casing are not transmitted to the inner casing.