Thalmann further comments that a full face mask is desirable for use with high oxygen mixes, as it allows the diver to be kept at depth until the convulsion subsides, and that a diver who loses the mouthpiece must be surfaced as he will try to take a breath when the convulsion stops, and on open circuit, that as long as the diver has the mouthpiece in place and is breathing, it should be left until you can get him out of the water, but should be removed on the surface if rescue breathing is necessary and possible. Furthermore, the main goal while the diver is in the water is to prevent drowning and secondarily ensure that the airway is open "after the convulsion stops" by keeping the neck extended.