A lifting bag is an item of diving equipment consisting of a robust and air-tight bag with straps, which is used to lift heavy objects underwater by means of the bag's buoyancy. The heavy object can either be moved horizontally underwater by the diver or sent unaccompanied to the surface.
It is advisable to select a lift bag with an appropriate capacity for the task at hand. If the lift bag is grossly oversized a runaway or otherwise out of control ascent may result. Commercially available lifting bags may also incorporate dump valves to allow the operator to control the bags buoyancy during ascent.
If a single bag is insufficient, multiple bags may be used, and should be distributed to suit the load.
Read more about Lifting Bag: Physics of Buoyant Lifting, Types and Construction of Lift Bags
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