Abstract: This invention relates to an articulated boom structure unit (15) adapted to be mounted on an ocean going lift barge (16) for maintenance of an offshore station (14), and having a platform (17) vertically movable relative to ocean floor engageable leg units (18); the boom structure (15) comprising a pedestal (23) mounted for rotation on the platform (17), with a first boom unit (26) pivotally mounted on the pedestal for vertical, pivoting movement, a mounting (29) supported on the outer end of the first boom unit (26) and held on a vertical axis, a second telescoping boom unit (32) connected at an inner end on said mounting (29) for movement in a horizontal plane, a third platform boom unit (33) mounted at an inner end to the outer end of the second boom unit (32) and having a parallelogram subassembly (34) as a part thereof movable upwardly and downwardly, and a personnel carrier (21) mounted on an outer end of the subassembly (34), which carrier (21) may be either a bucket or a work platform, with the carri