Abstract: An apparatus for use on a vessel and for gaining access to a fixed structure such as a marine platform. As shown a supply vessel (1) has located on the deck (2) a mounting (3) which is connected by a gimbal arrangement (30) to a support arm (4) carrying a boom assembly (5) with a capsule (6) for personnel. The arm (4), boom (5) and capsule (6) are controlled in position by hydraulic means (9, 31, 33, 36, 40, 41, 52) to be manoeuvred into a required position to transfer personnel to the platform or decking (7) for example. In order to stabilise the position of the capsule (6) relative to the platform (7) the hydraulic means (9, 31, 33, 36, 40, 41, 52) is dynamically controlled to compensate for movement of the vessel (1) such that the capsule (6) will remain substantially in the selected spatial position relative to the platform (7). The capsule (6) may include a control system which enables an operator to statically position the capsule (6) through control of the overall systems.