Ahh but life jackets in Jet aircraft are a classic example of where the perception overrides reality. As far as I know (happy to be corrected) there has never been a life saved by a lifejacket in a jet aircraft. Either the crash was not survivable or the passengers/crew survived without needing them eg the hudson river. But still every flight carries them and we are told how to put them on every time.....
Back to little aircraft and this is another example of where CASA requiring approval leads to less safe outcomes. Most good fitting, comfortable, crotch strap equipped lifejackets do no carry the CASA seal of approval. Try going for a swim one day in a pool in a casa approved lifejacket. Then imagine doing is in the open ocean in rough water, dazed and confused having just watched your aircraft sink beneath the waves. Try the same thing with a modern life-jacket unapproved for aircraft but approved for sailing and then tell me you would be happy with a CASA approved one.