A vessel is provided that is an improvement over previously disclosed jack-up rigs and lift boats. The vessel has at least three thrusters and is self-propelled. The vessel additionally has a raised and hollow crane support on which a crane may be mounted. The crane support is affixed to tracks, which permit the crane to slide along the deck of the vessel. The raised and hollowed feature of the crane support permits the storage of equipment and things beneath the crane support without hindering the movement of the crane along the tracks. Optionally, the vessel further comprises a sub-base structure removably affixed to the transom of the vessel; a base structure removably affixed to the sub-base structure; and a work-over rig removably affixed to the base structure. Also provided herein are methods of using the crane and affixing the sub-base structure, base structure, and work-over rig to the vessel's transom.