Operator was towing a wake surfer at approximately 10 MPH.  The surfer fell into the water.  There was no wake from other boats or wave conditions that affected the surfer.  The surfer did not strike the boat or the board.  The boat turned immediately to pick up the surfer.  The surfer was on her back but did not respond to verbal communications.  She rolled over in the water face down and two occupants of the boat jumped into the water, pulled her on board and turned her on her side.  She spit out water, but did not regain consciousness.  She was transported to the Cascade Hospital by private vehicle.  The officer suggested a CO test, but was told they did not have the means to complete that test.  The Dr stated he thought she had a concussion from hitting the water hard.  This would seem to be impossible as wake surfing is done at a very low speed of 10 MPH.  The other passengers on the boat stated that she went down for no reason.  The facts are as follows:  Slow speed incident; she turned over in the water to the point she spit water out when she was brought aboard (possibly turned over by the wake; no one can state she was conscious before that, as she did not respond to verbal communications); unconsious for a long period of time finally waking up in the hospital; no signs of trauma to her head or any where on her body.  With these facts I believe she was overcome by Carbon Monoxide.
Cascade                       