When scuba diver Dorian Borcherds turned on his video camera, he became transfixed by the giant translucent mass bobbing along beside him.
What he had captured on film in the watery depths off Papua New Guinea now has marine biologists excited.
The jellyfish was believed to be one officially sighted only once before off the coast of Far North Queensland — a quarter of a century ago — but it could also be a new species, a researcher believes.
The owner of a Kavieng-based scuba dive company, Mr Borcherds was diving with a customer in December when he spotted the strange creature and described it on social media.
"Saw a new type of jellyfish while diving today. It has cool markings and is a bit bigger than a soccer ball and they are quite fast swimming," he wrote at the time.
"I thought it was interesting as I had never seen one of these before, so I sent [the video] to my daughter who downloaded a jellyfish app," he said.
"It couldn't be identified, so she uploaded the footage to the app and within half an hour she had a very excited jellyfish expert on the phone from Tasmania."
That expert was Lisa-ann Gershwin from the Australian Marine Stinger Advisory Service, who at first thought it was the same jellyfish caught on the Great Barrier Reef in May 1997.
A small spotted jellyfish in blueish water
Screenshots from a video shot in 1997 of the original specimen that was found on the Great Barrier Reef.(Supplied: Queensland Museum)
"I was complete gobsmacked when they sent me through the photos," Dr Gershwin said.
"I thought, oh my God, what is this thing and where is it?
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"This species had only been spotted once on the Great Barrier Reef in the 1990s."
Chirodectes maculatus was first described in 2005 by a team of Australian scientists after they caught and preserved a specimen in 1997.
The scientists initially described the species as Chiropsalmus.
Dr Gershwin said she published another paper on the organism's classification a year later and officially moved it to the genus Chirodectes, where it was accepted.
After researching the video, Dr Gershwin worked closely with the Queensland Museum in Brisbane where the original Queensland specimen was stored.
"They sent me the video and I was able to go through it frame by frame," Dr Gershwin said.
"We compared the two separate jellyfish and I concluded that the one filmed off Papua New Guinea [by Mr Borcherds] is a new undiscovered species.
"I called Dorian and said, 'Are you sitting down?' and when I told him I thought it was a brand new species, he was very excited."
Dr Lisa Gershwin in a white tshirt holding a large box jellyfish by its bell in her right hand
Dr Lisa-ann Gershwin, who developed the jellyfish app, is one of the world's leading experts on jellyfish.(Supplied: Dr Lisa-ann Gershwin)
A new species?
While Dr Gershwin is convinced it is a new species, she is yet to submit her findings in a paper to be peer-reviewed.
"A new species is considered like a hypothesis, it has to be tested," she said.
"It's not technically discovered until it has been formally named and classified.
"I'm being very meticulous as I was involved in the re-classification of the original species, so I want to be more than right, I'm crossing every t and dotting every i.
"On top of that, we still have the mystery of where did the Great Barrier Reef specimen come from?"