A closed bell may be fitted with an umbilical cutter, a mechanism which allows the occupants to sever the bell umbilical from inside the sealed and pressurised bell in the event of an umbilical snag that prevents bell recovery. The device is typically hydraulically operated using a hand pump inside the bell, and can shear the umbilical at or just above the point where it is fastened to the top of the bell. Once cut, the bell can be raised and if the umbilical can then be recovered, it can be reconnected with only a short length lost. An external connection known as a "hot stab unit" which allows an emergency umbilical to be connected to maintain life support in the bell during a rescue operation may be fitted.