I can tell youfrom heart breaking experience thattime of useful consciousness (TUC) incold water is measured in short minutes with some variation for body composition and clothing.

Perosnal stories:
How about a Kansas school teacher that thought she would get a salt water souvenir from a crashing Northern California wave?
How about a tipsy fisherman whose boat went onto the jetty while he was in the toilet?
How about aoverturned, inexperiencedcanoeist whose body we never found?

Most people are not aware of the swift incapacitation that occurs ineven moderately cold water. As a frame of reference, we (USCG helo pilots/crews) arerequired towear dry suits anytime the water is below70 deg F and air temp is below 85 deg F.

Ifcold, coldwater is deep and wide, it might as well be lava.