Abstract: A combination offshore drilling rig which combines the desirable features of a slot-type drilling rig and a cantilever-type drilling rig while eliminating the limitations and undesirable features associated with either type of such rigs. The combination offshore drilling rig mounts the derrick and drilling equipment on a movable cantilever structure which may be positioned over a slot of sufficient area to permit the drilling operation to be carried out through the slot or may be moved outboard of the peripheral boundary of the rig hull to perform a drilling or workover operation outside the peripheral boundary of the rig hull.

Abstract: An improved barge hull for offshore drilling rigs is disclosed. The invention comprises a channel in the bottom of a barge hull extending from the bottom of said barge hull to the back of said barge hull for directing the flow of water under said barge hull to the back of said barge hull in order to disrupt the relative hydrodynamic stability of a body of water immediately behind said barge hull and thereby decrease the towing resistance of said barge hull.