In the late 60's I was diving professionally for abalone in "backstairs passage" between the mainland and Kangaroo Island and I have to say that looking up from the bottom at a surfer or wind surfer is like looking at a very easy "free meal" from a sharks point of view AND believe me when I say that there are many VERY big bighties that regularly pass through that stretch of water. I would comfortably dive with them UNDER water but I wouldn’t swim, surf, or windsurf, on the suface there EVER, even sailing a cat there is not without its concerns to me.