Hang on a minute. First you said they were putting their heads into the (non existent) arm holes, now they are not putting their heads into the necessary (and only) hole.
In the case of the Hudson incident most people would only have grabbed their vest in the very few moments prior to the landing, some were known to have been donning the vest either whilst leaving the aircraft or even after leaving.
Admittedly the cases in which vests are thought most likely to be used are where there is adequate time prior to a ditching for all to don the vest. They have only one hole to avoid confusion though the straps can be confusing.
In the unlikely event of a successful ditching on the open ocean the greatest problem would be to ensure passengers do not inflate their vests before leaving the aircraft, doubtless with their belongings if the attitude of some poster on here is typical.
Last edited by philbky; 8th Mar 2015 at 00:40.