The incredible annual coral spawning event has been taking place on the Great Barrier Reef over the past few days.

The first reported sighting of the spawning occurred on Sunday with guests on board Port Douglas dive and snorkel boat Poseidon treated to the natural phenomenon.

"Guests were thrilled to experience an annual coral spawning of a boulder coral whilst snorkelling at the Agincourt Ribbon Reefs," said Poseidon's Steve Edmondson (pictured), adding conditions need to be just right for event to occur.  

"Corals traditionally spawn at night, five nights after the full moon in December and water temperatures need to be consistently 27-28 degrees."

Divers visited Low Isles last night to catch a glimpse of the spawning, which has been described as looking like an "underwater snowstorm" and brings new life to Great Barrier Reef.

One of those to see the action up close was Tropical Journeys' Chris Jones.

"It was an awesome night. There was a fair bit of soft coral that spawned and a little bit of stag horn coral, the marine life out there was stunning, it was just a beautiful night," he said.