Quite an interesting thread this.
Airlines ask for cabin crew to be confident swimmers, it's not cross channel stuff because if you ditch in the sea it's better if you don't swim. But if your confident in the water you can concentrate on other things besides just trying to stay afloat. It's not very nice in the water even if you have a life jacket on.
Years ago I did some sea survival training relating to my work in the yachting industry. This time of year in the Northern hemisphere the sea is at it's coldest. Unless you are kitted out in a full fighter pilot style immmersion suit your not even going to SURVIVE in the water more than 10 minutes and if you start swimming you live even less time.
Most ditchings are probably going to happen just after take off or just before landing so hopefully your in shallow water and rescue is not too far away.
Rule must be only ditch in the Maldives.
On the point of rear facing seats I seem to remember a while back being told this was not possible because if an overhead locker burst open on impact and the contents fell out the injuries to the passengers would be facial rather than the back of the head which can to an extent withstand greater impact.