Abstract: A floating marine structure, such as a drillship (10 ) includes at least one thruster (14, e.g.) which includes a thruster head (22) having a propeller (102) which is adjustable to vary the angular relation to the drillship hull (11) of the horizontal direction of thrust produced by operation of the thruster. The thruster includes an enclosure (23) above the propeller for a propeller drive motor (49). The thruster has a deployed position in which the propeller (102) is submerged below adjacent exterior surfaces of the hull. The thruster is retractable vertically into the hull to retracted position where the propeller is below the floating waterline (50) of the hull. Further, the thruster has a more elevated service position to which the thruster is movable vertically from its retracted position.