The standard PFDs are bulky and awkward to wear. There are 'working' type PFDs with handy pockets that are somewhat better, but they are not readily available and are a bit pricy. The best compromise is a float coat which works very well when things are a bit nippy out on the water. models with a beaver tail will also do a better job of conserving body heat, a job at which the typical PFD fails miserably. in cold water, a PFD is nothing more than a handy marker for those retrieving bodies.
WRONG!!!As the Canadian Dr. Gordon Geisbrecht (aka "Professor Popsicle") has repeatedly demonstrated,
with flotation you won't become unconcious from hypothermia in cold water for about an hour. However, swim failure occurs in ~5-15 minutes, and without flotation you will drown at that point. The vast majortiy of "hypothermia" deaths in cold water aren't hypothermia at all. They are simply drownings, from swim failure due to chilling arm and leg muscles. Even with a PFD you can't stay in cold water indefinately, but you can survive at least an hour, and maybe much longer. This greatly increases your chances of being rescued.
Prof. Popsicle has developed the "1-10-1" principle of what happens in cold water immersion:
Cold Shock (gasping,hyperventilation) last about
One Minute.
Swim Failure (due to chilling of your arm and leg muscles) in about
Ten Minutes. Without a pfd you drown at this point.
Unconscious due to Hypothermia (takes this long for your core to cool) in about
One Hour.
See
http://www.umanitoba.ca/faculties/kinrec/about/giesbrecht.html for more information about Dr. Geisbrecht. In particular follow the links to "Cold Water Boot Camp" and to the Discovery Channel Canada link on "Cold Water Survival". Both these have some graphic examples of how long one can survive in cold water
WITH A PFD.
For more information on hypothermia, see the current Alaska Cold Injuries Guidelines for EMS (developted in part by Dr. Geisbrecht) at:
http://www.ems.alaska.gov/EMS/documents/AKColdInj2005.pdfFor a recent example of how several girls (wearing PFDs) survived two hours in 40-45 F water see:
http://www.alaskadispatch.com/article/kenai-girl-credited-saving-friends-tustumena-lake-accidentAlso note that modern PFDs developed for sea kayaking and white water kayaking are very easy and comfortable to wear. For other kinds of boating, the new inflatable PFDs are even less unobtrusive.
There is no longer any excuse for not wearing a PFD!