Hopefully adding to the thread, ditching/floatation kits were discussed
here with this piccy.
and also
here
There is a film around showing the Lynx floatation kit trials that I once saw on a flt safety course or maybe it was at the dunker, Yeovilton. They weren't meant to keep her afloat, but to allow time for crew to escape. If all the bags went off ok then it was fine, but if not she behaved unpredictably. When she started to go down, it was 'shockingly rapid'.