The requirements for becoming an offshore crane operator tend to vary by the particular employer. Some require for crane operator candidates to have acquired an offshore crane operator certificate or to hold a helicopter landing officer certificate or restricted cardio operator certificate. Some also strongly require for one to have previous experience in the oil industry field. For example, most of the times the Maersk Drilling corporation chooses to hire crane operators that have experience as assistance crane operators or gas roustabouts. Additionally, the majority of offshore drilling jobs, which includes crane operator, require for workers to be able to carry out several-day or several-week shifts at a time.