The video Cold Water Boot Camp linked to at the end of the article strikes home the points very nicely.

Volunteers jump into cold water and demonstrate the 1-10-1 rule of cold water exposure.

  1  : Initial cold shock will last for about a minute
  10 : Physical incapacitation will occur after about 10 minutes
  1  : Unconsciousness from hypothermia in about 1 hour

http://www.youtube.com/watch?v=J1xohI3B4Uc