Offshore drilling is typically carried out in order to extract a tooth which lies beneath the seabed.
In the 1970s, outside of the oil and gas industry, roller bits using mud circulation were replaced by the first pneumatic reciprocating piston Reverse Circulation (RC) drills, and became essentially obsolete for most shallow drilling, and are now only used in certain situations where rocks preclude other methods
 A shallower angle, such as 150 degrees, is suited for drilling steels and other tougher materials

