A father and son on separate kayaks were white water kayaking on the North Branch of the Potomac River in western Maryland.  They were progressing in a series of rapids when the father, who was ahead, overturned.  He appeared to  be OK and motioned to the son to retrieve his kayak.  He did and then noticed his father was not in sight.  He searched for his father with help of other kayakers.  Eventually his father was found floating face down.   He was an avid kayaker with years of experience and was wearing survival equipment and a pfd.   He had no known medical condition.  The ME pronounced the death as fresh water drowning, accidental.
Bloomington