buoyancy aid and encouraging the casualty to help themself. If contact must be made, the rescuer should try to approach the casualty from a direction that presents least risk to the rescuer, such as from behind. Alternatively, the rescuer may need to wait until the casualty is incapacitated before approaching. Incident management In a professional diving operation, management of any rescue or other emergency is the responsibility of the diving supervisor. In a recreational scenario, it may be the responsibility of the Instructor, dive-master or boat skipper, if professionally involved. In many recreational incidents there is no specific person responsible for the safety of others, and a rescue is often managed by the person best able to deal with the situation on site. When the rescue involves a group of people, co-ordination is needed to make it quick and effective. This may be carried out by the skipper of the boat, if diving is taking place from a boat, or by a diver. Some training agencies offer courses to prepare divers for such as role, for example BSAC's Practical Rescue Management course. Equipment Diver rescue may involve equipment used underwater and equipment used in the recovery of the diver from the water and subsequent first aid and transportation to a suitable medical facility. Rescue tether Surface supplied standby divers and bellmen may carry a short length of rope with a clip on each end to support a disabled diver from the rescuer's harness, to allow the rescuer the use of both hands during the recovery to the bell or the surface. Oxygen administration equipmentAdministration of 100% oxygen at the surface is indicated as first aid for a large range of diving related conditions, and is not, as a general rule, contraindicated for any person medically fit to dive. If the diver is conscious and breathing spontaneously without difficulty, a demand regulator supply is convenient and economical of the gas supply. A demand valve can deliver about 95% oxygenWith a well-sealed mask. Non-rebreather masks provide a constant high flow rate of oxygen, usually from 10 to 15 litres per minute, which can be manually set to just sufficient to prevent the reservoir bag from emptying on the average inhalation. For casualties who are not breathing spontaneously, or who are breathing with difficulty, Bag-valve masks and manually triggered ventilators may be used to administer positive-pressure ventilation. Effectiveness of all delivery systems depends