[aka HKGpax]
Erm, unless I am mistaken, in the whole history of commercial jet aviation there has only been one successful attempt to ditch a big jet in the sea (and quite a lot of failed - as in almost no survivors - ones). Since everyone has lifejackets anyway I can't see that swimming needs to be very high on the requirements list.
And by the way, I'm surprised the airlines don't complain mightily about carrying all the lifejackets and stuff which must cost a fortune in fuel and have saved very very few lives. The cost benefit analysis must put that at many millions of dollars per life, which could surely be much better spent on, for example, ground control radar at airports which don't have them.