Abstract: A marine turbine and tower combination in which the turbine is mountable on the tower, The turbine has a co-operating member to interact with the tower to enable the turbine to be mounted on the tower in a pre-determined alignment. In one arrangement, the support tower comprises a substantially horizontal thruster plate mounted on top of the tower. The thruster has a central aperture to receive a downwardly directed stud on the turbine the thruster plate providing lateral support for the turbine. The stud has a vertical reaction interface around a lower part of the stud which is supported vertically by a reaction ring mounted on the tower.