A buoyant structure contains a hull. The hull has a main deck, a lower inwardly-tapering frustoconical side section that extends from the main deck, a lower generally rounded section extending from the lower inwardly-tapering frustoconical side section, a generally rounded keel, a fin-shaped appendage secured to a lower and an outer portion of an exterior of the keel, and an offloading device slidably connected to an outside surface of the hull configured for rotating around an outer circumference of the hull.