Abstract: A propeller assembly, a so-called rotatable thruster, for propelling, manoeuvering, steering and/or positioning a watercraft, floating docks, pontoons and in particular offshore platforms, includes a propeller (1) having an embracing propeller shroud (2) and mounted on a propeller shaft journalled in a gear housing (3). The gear housing accommodates a bevel gearing through which the propeller shaft is connected to a drive shaft extending through a tubular support strut (4), which is connected at its lower end to the gear housing in order to support the same. The upper end of the support strut is arranged to be rotatably mounted in an opening in a bottom part of the hull of the watercraft, with the propeller shaft extending substantially horizontally, so that the drive shaft can be connected to drive machinery located within the hull and such that the assembly can be rotated about a rotational axis coinciding with the axis of the drive shaft, by means of rotational machinery located within the hull.