This may not be relevant to the latest attack, but for the bigger GWS issue...
It seems that Killer Whales and GWS' aren't the best of friends.
This guy surmises what happened...
http://www.discoverwildlife.com/forum/the-whale-that-ate-jaws-t10816.html
dude on forum said...
Also discussed was the fact that, after the attack, all of the great whites vanished.
...in what was documented in this National Geo show;
natgeotv.com/uk/the-whale-that-ate-jawsPerhaps transmitting Killer Whale sounds from little solar powered sound units, mounted on offshore buoys would get the Great Whites to keep their distance?
But then perhaps that might attract Killer Whales and only swap one problem for another?