One of the greatest underwater marvels of the world is happening again right here, right now.

Migaloo the white whale has been captured in a stunning video by the crew of Big Cat Green Island Reef Cruises earlier today.

And it's a magical, awe-inspiring sight to see.

Big Cat skippers John and Patt filmed Migaloo as the gentle giant swam and frolicked off Green Island.

"Our skipper saw a pod of black whales so stopped the boat, these whales headed towards MV Reef Rocket and out of nowhere Migaloo appeared," the reef operator said.

"We had some very lucky passengers travel with Big Cat Green Island Reef Cruises today! Thanks to our skippers John and Patt for this awesome footage."