The Warilla man has lived all of his 78 years by the lake and said it was not the first time sharks had ventured inside.

"I can remember about 60 years ago when there were six sharks in the lake," he said.

"It was this time of year and there had just been a king tide, I think that caused them to get trapped."

Sympathetic to the sharks' plight, a teenage Mr Graham watched on as residents made ungainly attempts to kill the bewildered animals.

"These sharks were swimming from the entrance to the bridge, up and down, they weren't trying to hurt anyone," he said. "This one fella was big-noting himself, standing up on the launch with a spear watching for the sharks.

"His boat hit some sand and he fell in the water, he was terrified and scrambled back into the boat."

The marooned sharks died a week later, and a curious Mr Graham helped bury the fascinating creatures.

"They were all about 3.6m long or a little bigger and they would have been about 1m wide," he said. "I opened one of their mouths for a look and a man could have fitted inside.

"It had six rows of teeth, I was quite surprised."

Mr Graham believes the sharks may have been grey nurses.