Emergency and wildlife rescue services and a team of bystanders fought in vain to save the adult female dolphin, which was found injured and distressed on the beach south of Bellambi boat ramp.

Morning walkers Tim McGoldrick and Terri Evans sparked the passionate rescue effort, after finding the common dolphin on the sand, bleeding from its fin, tail and mouth.

"I came around the point and I could see this thing moving, so I went to look at it," Mr McGoldrick said.

"It had been there a little while, I think, because it was right out of the water and it had dug a bit of a hole with its flipper in the sand."

After unsuccessfully attempting to release the animal back into the ocean, Mr McGoldrick - with the help of Mrs Evans' husband Craig - used a tarpaulin to carry the dolphin to the boat ramp.

There, several National Parks and Wildlife rangers, police rescue officers and others worked to stabilise and examine the mammal.

NPWS ranger Anita Zubovic said it was likely that the dolphin was sick, because it was highly unusual for common dolphins to swim close to the shore.

The examination showed the dolphin was taking only seven breaths per minute and was struggling to keep its balance.

After more than two hours, rescuers attempted to use a seaweed-packed stretcher to transport the dolphin to a Wollongong vet for further examination. However, it died on the way.

Veterinary surgeon Michael Cannon performed an autopsy and confirmed the dolphin had died of suspected pancreatic cancer.

"It had a (mango-sized) mass that was pressing on its intestine, and it hadn't eaten anything for days or maybe even weeks," Mr Cannon said.

"I think this animal just got so weak from lack of food that it started to lose its balance and it knew it couldn't support itself so (it beached itself)."