A tour group on a sightseeing cruise to Ningaloo Reef off the coast of Western Australia became witnesses to an epic battle between a pod of killer whales and humpback whales defending their young.

Boat operator Prue Wheeler said the orcas killed two out of four baby humpback whales in the attack that lasted for five hours.

“To see firsthand a successful and an unsuccessful kill for the killer whales was incredible,” she told Storyful.

“With the humpback whale protecting her newborn calf on her back – lifting her out of the water and using the shallow reef in her favour – while watching the orcas working in pack formation, will be something none of us there will ever forget.”

This video shows the hunt, while amazed passengers on the SV Keira commented on the spectacle. Credit: YouTube/SeaLife Differently SV Keira