What
really do the students
needto learn from practising CESA....
1. At the surface, they can breath
2. They should ascend at a safe speed.
3. They should exhale slowly on ascent.
4. They should establish postive buoyancy immediately on surfacing.
I think a lot of dive instructors over-complicate this skill. It's pretty damn easy. Basically, a
normal ascent, but with exhalation throughout. That is all.....
There can be endless debate about whether it should be practised with full lungs, empty lungs blah blah..... but there is no way to prepare the student for every possible contigency or scenario. Just concentrate on getting them to ascent without breath hold, because in a real emergency, that is all they need to be able to do...and of course, get buoyant on the surface.
I think that the real, tangible, benefit of practising CESA is that it illustrates, to the student, how dangerous it is to run out of air. When students struggle with 6-9m CESAs, I always get them to think about how it would be to perform that from 18m or 30m or 40m..... I then can compare it with conducting an AAS....