Derrick: The tower-like structure that houses most of the drilling controls.
Drilling rig: A derrick and its associated machinery. A drilling unit that is not permanently fixed to the seabed, e.g., a drill ship, a semisubmersible, or a jack-up unit.
Jack-up rig: A mobile offshore drilling rig with legs lowered to the ocean floor as an anchor. Once the legs hit bottom, the body of the rig is “jacked up” above the surface of the water. These rigs are used in shallower applications for drilling, workover, or completion.
Semisubmersible rig: A mobile offshore drilling rig that floats partially submerged.
Submersible rig: A mobile offshore drilling rig with compartments that are flooded to cause the structure to submerge and rest on the seafloor; used in shallow water.