supply is compromised. Bell abandonment – Surfacing from a disabled wet bell Surface gas supply failure – Switch over to on board gas supply by bellman in the event of a surface gas supply failure. Voice communications failure Light and gas signals for surface supplied dives Contaminated surface gas supply – Switch over to on board gas supply by bellman in the event of suspected contamination of the surface gas supply . Closed bell emergency procedures: Bell umbilical failure - Switch over to onboard gas supply, emergency signals and prepare to surface Dynamic positioning alarm and runout response Main lifting wire/winch failure – Alternative lifting possibilities include the clump weight winch, other hoisting equipment on the platform, and if rated for lifting, the bell umbilical. Through-water transfer at depth to another bell may be possible. Loss of bell internal pressure – Rescue procedures These are procedures that the professional standby diver must execute when deployed to go to the assistance of the working diver in an emergency, or the buddy or dive-team member in a recreational or technical dive should use if another member of the team is unable to manage an emergency themselves. They are also emergency procedures, but for another person's benefit. It is fairly common for a diver never to need to apply one of these procedures for real, and they too should be practiced to maintain skill levels. Professional diving organisations typically require periodical emergency exercises as specified in their operations manual to maintain these skills. Rescue procedures include following the umbilical or lifeline to the distressed diver, providing emergency breathing gas, recovering the casualty to the bell or surface, releasing a snagged umbilical, umbilical changeout at depth, providing the supervisor with continuous updates. Rescues are generally done in unexpected circumstances, and seldom follow the text-book example, so the rescue diver often has to modify the learned response to suit reality. Scuba diving rescue procedures: Locating the casualty underwater – Searching for the disabled diver. Providing emergency gas – Providing emergency breathing gas to another scuba diver Freeing the trapped casualty – Assisting an entrapped or snagged diver to get free. Managing a convulsing casualty – Recovering a diver who is convulsing underwater to the surface Bringing the casualty to the surface – Getting the diver to a place where first aid is possible Controlled buoyant lift – Lifting an incapacitated diver to the surface Making