and recover it to the chamber system. The system used to transfer the bell on deck may be a deck trolley system, an overhead gantry or a swinging A-frame. The system must constrain movement of the supported bell sufficiently to allow accurate location on the chamber trunking even in bad weather. A bell cursor may be used to control movement through and above the splash zone, and heave compensation gear may be used to limit vertical movement when in the water and clear of the cursor, particularly at working depth when the diver may be locked out and the bell is open to ambient pressure. gear may be useful to place the bell closer to the worksite if the ship cannot safely approach it to a convenient distance Moon pool A moon pool is an opening in the base of the hull, giving access to the water below, which allows divers, diving bells, remotely operated underwater vehicles or other equipment to enter or leave the water easily and in a relatively protected environment. Diving from a DSV Diving from a DSV makes a wider range of operations possible, but the platform presents some inherent hazards, and equipment and procedures must be adopted to manage these hazards as well as the hazards of the environment and diving tasks. Hazards Hazards of the positioning system Anchor patterns Thrusters Equipment On board recompression facilities Equipment to transport the diver through high risk zones Equipment to limit access to known hazards Hyperbaric evacuation facilities Procedures Use of stages and bells to transport the diver through the interface between air and water, to avoid hazards, and for decompression. Surface-supplied diving with limited umbilical length Underwater umbilical tending See also References External links Diving support equipment Ship types