You would think being a shark you wouldn't have to watch your back.  As the sea's ultimate predator, sharks patrol the ocean safe in the knowledge that they rule the waves.  But now it seems sharks shouldn't swim so easy, as their bigger, hungrier couins might view them as a tasty snack.

Australian researchers snapped this extraordinary sight in August while they were carrying out a census of fish off Great Keppel Island off the Great Barrier Reef

This is believed to be the first time scientists have ever photographed a shark eating another shark.

Australian researchers snapped the extraordinary sight in August last year while they were carrying out a census of fish off Great Keppel Island off the Great Barrier Reef.

The experts, from the Australian Research Council's Centre of Excellence for Coral Reef Studies, knew sharks ate other sharks after discovering remains in the stomachs of carpet sharks, but it is the first time the process has been photographed in action.

The photo shows a type of carpet shark called a tasselled wobbegong, munching on a brown-banded bamboo shark head first, thanks to its remarkable ability to dislocate its jaw

They estimate it would have taken the carpet shark several hours to finish its snack.

Carpet sharks look flat and have carpet-like patterns on their bodies. They spend much of their time lying on the ocean bed waiting for passing food.

Usually they like to feast on small fish or invertebrates.

Researchers said that during the 30-min observation period, neither shark moved position and the wobbegong did not further ingest the bamboo shark.

'We assume that it would have taken at least several more hours to completely consume the bamboo shark.'