the rescue more efficient. Methods of attracting help include shouting, waving a straight arm, flag or surface marker buoy, blowing a whistle, flashing or swinging a torch/flashlight at night, or using a strobe at night. Cylinder powered, high-pressure gas whistles may be effective even over the sound of engines. Carrying out artificial ventilation in the water If the casualty is not breathing, it is possible to sustain respiration or even restart it by artificial ventilation (AV) at the surface of the water. It may be difficult for the rescuer to assess breathing, but it is more likely that this would fail to indicate shallow breathing than a false positive, and as there is little risk of harm from an attempt to administer rescue breathing when it is not needed, there is no reason to not administer AV if there is any suspicion that the casualty in not breathing. Methods of in-water AV vary depending on diver training organization: The BSAC technique works like this: the casualty and rescuer are buoyant the rescuer is positioned at the side of the casualty's head facing the ear the rescuer extends the casualty's neck and closes the mouth by lifting the chin with one hand the rescuer pushes the casualty's far shoulder upwards with the other hand causing the head to twist towards the rescuer the rescuer makes a seal over the casualty's nose using the rescuer's mouth and exhales to fill the casualty's lungs the rescuer aims to do 10 inflations per minute if stationary, 2 inflations every 15 seconds if towing It is not possible to provide effective cardiac compression in the water, and it is also unlikely to reliably identify cardiac arrest in the water. Towing the casualty If the casualty is incapacitated or exhausted, help is needed to move the casualty to safety. Towing is time-consuming and will exhaust the rescuer, especially in rough water, currents, or if the rescuer is wearing high-drag equipment such as a drysuit or carrying bulky equipment. It may be possible to avoid a tow by using a boat to pick up the casualty and rescuer. Alternatively, ropes thrown to the rescuer can be used to pull the pair towards safety. Removing the casualty from the water Urgently lifting an injured or incapacitated casualty from the water is a significant problem especially where there are few rescuers, the sea is rough, the boat has high