HUNTING sharks that have killed humans is usually useless and potentially dangerous, marine experts warned yesterday. Professor Brian Morton, director of the University of Hongkong's Swire Marine Laboratory, speculated that the killer was a tiger shark, a species which usually travels in groups. As Vic Hislop, an Australian shark hunter, continued his search for a man-eater, Professor Morton said: ''Supposing this guy gets one, supposing he gets two - do we know how many there are?'' The killing of one shark could give swimmers a false sense of security, prompting them to return to the water before it was safe to do so. ''What are you going to do - kill all the sharks in the world?'' Professor Morton asked. He said the idea of solving the problem by hunting one shark returns to the days of the film Jaws, in which the killer was a single, demonic creature. Michael Stewart, curator of Ocean Park's aquarium section, said there were about 25 shark attacks each year around the world. ''You're probably more in danger standing outside of a jewellery shop on Nathan Road than you are from a shark attack,'' he said. Mr Stewart said Mr Hislop's shark hunt feeds public paranoia. ''He seems to be sensationalising the whole issue,'' he said. It was ''very probable'' that Mr Hislop would catch the wrong shark. But even if the killer shark were caught it may have already digested its victim, he said. ''I've got nothing against [Mr Hislop]. He's a damn good fisherman. But this type of revenge killing is becoming less and less popular because people are respecting that we need to preserve our ocean life,'' he said.