The humpback whale was spotted earlier in the day, washed onto rocks at South Broulee beach.

A rescue mission was being organised when the whale washed back off the rocks.

"Twenty minutes later a massive shark came in and just took half of it," Far South Coast director of surf lifesaving Andrew Edmunds said.

"The beach is now closed and is likely to remain so for the rest of the afternoon. We are advising people to be cautious and stay away from the water."

The Westpac Lifesaver 3 helicopter was sent to Broulee about 3pm because of concerns a large school of sharks was feeding on the whale carcass at South Broulee. It returned to base by 3.40pm after spotting two sharks.

Two 3.5 metre sharks sighted off Sth Broulee Beach by Lifesaver 3. Beaches closed nearby, no swimmers in danger. pic.twitter.com/8FMiisaV16 — Westpac Life Saver (@Lifesaverhelo) January 7, 2015

More than 200 people were on the rocks earlier in the day .

"They have been moved on and police are trying to keep people away from the area."

Experts from ORRCA - Marine Mammal Rescue and Research - Australia, along with representatives of the Marine Park Authority, arrived on the scene about 3.15pm.

A National Parks and Wildlife Service spokesman has confirmed the whale taken by a shark was a sub-adult humpback whale.

"They grow very quickly from birth [3m] to 8-10m within about two years," he said.

"This one looks in very poor condition which is very likely the reason it beached. The sharks are just doing what sharks do. They are sometimes called the garbage men of the sea - they help keep the oceans clean by consuming carcasses of dead animals."

- Batemans Bay Post