Steering; Slowing-down otherwise than by use of propulsive elements; Dynamic anchoring, i.e. positioning vessels by means of main or auxiliary propulsive elements
Steering or dynamic anchoring by propulsive elements; Steering or dynamic anchoring by propellers used therefor only; Steering or dynamic anchoring by rudders carrying propellers
Propulsive elements, other than jets, substantially used for steering or dynamic anchoring only, with means for retracting, or otherwise moving to a rest position outside the water flow around the hull
