A water flow turbine arrangement for capturing energy from water flows is provided. The arrangement includes: a base member (212); a generally open support structure (210) mounted to the base and upstanding therefrom, the support structure including plural legs (216) joined by a cross brace at or adjacent their upper ends; an electrical generator (230) mounted to the base; and shaft mounted turbine blades (220) mounted for rotation generally within the space occupied by the legs about a turbine axis. The turbine shaft (222) is supported at its upper end by the cross brace and is coupled to the generator at its lower end by a magnetic torque transmitting coupling, allowing complete fluid sealing of the generator's housing.