i have been an avid diver for several years now but lately i seem to have a harder time holding my breath "due to asthma" and anxiety usually kicks in, i normally like to dive in waters that do not exceed 20ft, i do alot of spearfishing at night along the reefs and sometimes outside of the breakers, My question is.....would somthing like an iflatable pfd be a good insurance in the event of an emergency, i normally dive with several partners but at night keeping track with one another can be very difficult. i am looking at a unit called Sospenders: http://www.landfallnav.com/sospenders.html, ifigured in the event of an asthma attack or any other emergency this would be a good unit for back up, what do you think, thanks