There is a man-made lake in Seattle where one can rent windsurfer boards. It is a small lake but some years ago a guy fell off his board, it hit him in the head and he drowned.
Probably paddle board could cause the same situation.
As I just responded to someone else....according to a Jesse Waters segment, autopsy revealed no injuries. If he got hit in the head with a paddle board, enough to knock him out, there’s going to be a mark and that injury would only get worse under water.
Also, see comment #28, if you care to get another perspective.