The windsurfer who died was under his sail when his friend jumped in the water to help him
He was wearing a buoyancy vest when he was rescued
His friend took his head out of the water as quickly as possible
Many of us who's windsurfed have had some scary calls pinned under the sail in good size surf
Sometimes getting stuck in the harness line to make matters worse
Sometimes swimming the long way out...along the luff of the sail
The buoyancy vest could be a big culprit here as it would keep you from diving underwater to get away from the sail
I windsurf and doubt that was the reason because you don't dive underwater, you just swim or pull yourself to the edge of the sail or the sail past you. Usually snagging wouldn't happen with a buoyancy vest either.
Its rare but it happens for a windsurfer to be spun during a fall and the harness line to get twisted around the spreader bar hook. Then you can be in big trouble - especially if waves are washing the gear around. Most drownings under a sail, that would be the cause IMO.
He may have been unconscious or some other condition may have prevented him from getting out.
We haven't even heard what it was that hit him.