of water into the lungs. There is no evidence that compressing the chest to promote exhalation is more effective than simply maintaining an open airway. Managing a convulsing casualty Convulsions due to acute oxygen toxicity may render a diver unconscious. A common symptom is convulsions similar in appearance to epileptic seizure. US Navy Diving Manual Revision 6 The US Navy Diving Manual Revision 6 Volume 4 section 17.11.1.4 recommends the following procedure for managing a convulsing casualty at depth. This differs significantly in some details from the procedure recommended by Dr E.D. Thalmann on the Divers Alert Network website. The rescuer should assume a position behind the convulsing diver. The casualty's weights should only be dropped if progress to the surface is significantly impeded. (Thalmann recommends releasing the weights unless the diver is wearing a dry suit, as the dry suit without weights may cause the diver to take a face down position on the surface.) The ascent should not be started until the convulsion subsides (Thalmann makes no recommendation to delay the ascent.) The rescuer should open the casualty's airway and leave the mouthpiece in their mouth. If it is not in their mouth, the rescuer should not attempt to replace it. A rebreather mouthpiece that is not in the mouth should be switched to "Surface" position, so that the loop does not flood. (Thalman makes no mention of opening the airway, possibly on the assumption that air will escape without this manoeuvre.) The casualty should be grasped round the chest above the breathing apparatus or between the breathing apparatus and their body. If this is difficult, the best method possible to obtain control should be used. A rebreather should be flushed with diluent to lower oxygen partial pressure and depth maintained until the convulsion subsides. (This step is significantly omitted by Thalmann.) The rescuer should make a controlled ascent to the first decompression stop, maintaining a slight pressure on the diver's chest to assist exhalation. If the casualty regains control, the divers should continue the ascent with appropriate decompression. (omitted by Thalmann) If the diver remains incapacitated, the rescuer should surface them at a moderate rate, establish an airway and treat for symptomatic decompression illness. (omitted by Thalmann) If additional buoyancy is required, the rescuer should inflate the casualty's buoyancy compensator. The rescuer should not release their own weight belt or inflate their own buoyancy. On reaching the