Airwave, interesting take on the rebreather. When I did my dunker drill the time before last we had a go with them and I thought they were great, really taking the pressure off the rush to get out, and not forgetting that in the real world of cold cold sea, the gasp reflex is very powerful. I had done a little bit of scuba diving so for me, the concept of breathing underwater was not alien. I was rather jealous that the pax got them it we didn't.