Aerial shark patrols have been stepped up at the ISAF World Sailing Championships after a large great white was spotted in the area where the competitors launch their boats each day. The aerial patrols over the sailing courses were increased on Wednesday, in response to Tuesday evening’s sighting of the shark in the Fremantle Fishing Boat Harbour, where the boat park for the championships is based.With three fatal shark attacks in the southwest of Western Australia in recent months and several near misses, organisers were already hypersensitive to the threat posed to competitors prior to the sighting.Event director John Longley briefed international sailing teams on the sighting on Wednesday morning.