Artist Jenny Richardson of Mirrabooka said the shark had threshed about in the shallows and seemed intent on reaching the beach where it remained high and dry.

‘‘It was the saddest thing I’ve ever photographed,’’ Ms Richardson said.

Mirrabooka resident Angus Picker and his 22-year-old son, Ben, were among the people who tried to return the giant fish to deep water in the hope of saving its life.

‘‘We tried to tow it into deeper water and moved it around to get some water into its gills and revive it but I could feel the shark had all but spent its energy. We never considered ourselves to be in any danger, I don’t think the poor thing had the energy to bite. We could feel the life leaving it,’’ Mr Picker said.

Mr Picker measured the shark and said it was a good nine feet (2.74 metres) long.

‘‘There was damage to its dorsal fin and I suspect it had been hit by a boat and had suffered internal injuries. Inititially it threshed around in the water like a mad thing. It seemed intent on beaching itself to die,’’ Mr Picker said.

‘‘I used to let my kids water ski in the lake but after that chap’s boxer dog was taken last year when his owner threw a stick into the water, I put a stop to the kids going into the lake.

‘‘Those people who think there’s no sharks in the lake should take a look at this,’’ he said.

A few years ago most people in Macquarie didn’t believe stories of sharks in the lake, but many lakeside residents now say shark sightings have multiplied since commercial fishing stopped in Lake Macquarie.

Taronga Zoo shark expert John West said the shark appeared to be a great hammerhead species.

‘‘The dorsal fin looks to have been cut and has flopped over to one side, but I don’t think that would hinder it at all,’’ he said.

Mr West said any shark more than two metres long could ‘‘potentially bite if harassed’’ but said there had never been any unprovoked hammerhead shark attacks in Australia.