Have there been any documented cases of serial killers who targeted boaters?
I'm putting together a list of known hobbyist serial killers.

I imagine bird watchers would be easy to off in the woods, kite flyers could
be decapitated with kite lines, scrabble players could be asphyxiated with
scrabble pieces, bridge players could be lying dead in the cardinal
directions, stamp collectors could have their faces glued on to albums,
fishermen could be gutted, paintballers could be shot with real guns,
yachters could have their skin flapping in the wind.