Maritime Museum curator Paul Mazourek found the young Port Jackson shark preserved and stuck between two rocks last month.

"It's amazing," he said.

Mr Mazourek believed the young adult died from natural causes, because there were no puncture wounds.

He said it was preserved through a "natural mummification" process, which combined regular and repeated exposure to salt water and sun.

Because the shark was trapped between the rocks, this caused it to be exposed to the sun during the day and then washed over by water as the tide came in.

The shark is now on display at the museum among only two other "mummies" found locally.

They include a large stingray, also found by Mr Mazourek, and a baby Port Jackson shark.