Volunteers had prepared to camp overnight to monitor and rehabilitate the 3.5-metre dolphin, which was first spotted by lifeguards just before 10am but is thought to have been stuck for at least an hour before that.

Ronny Ling, president of Organisation for the Rescue and Research of Cetaceans in Australia (ORRCA), said volunteers from the mid-north coast to Sydney had moved the dolphin from Redhead beach into a lagoon near Third Creek to recuperate.

"Volunteers will be monitoring the dolphin throughout the night to make sure it gets its orientation back and checking its breathing and heartbeat for stress," he said.

A vet had said the dolphin, which had abrasions over its body, would not need to be euthanised. But the animal's condition deteriorated around 7.30pm and it died.

Mr Ling explained that being beached had taken a "huge toll" on the male dolphin.

"It's the equivalent of a human being put in a box for three hours," he said of the dolphin's ordeal.