The incredible moment an octopus puffs up like a parachute - and researchers can't decide if it was hunting or just angry

An Australian diver filmed the moment an octopus suddenly puffed up
She thought that the octopus tried to intimidate and scare her way
But researchers can't agree on what caused it to exhibit this strange behaviour
Some researchers think the octopus was pushing water on the seafloor to chase prey out of their hideouts, others think it puffed up to try to scare the diver away

Published: 14:01 EST, 2 February 2017 | Updated: 16:14 EST, 2 February 2017

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An Australian diver filmed the moment an octopus suddenly puffed up, inflating itself with water.

She thought that the octopus was trying to intimidate and scare her away, but researchers can't agree on what caused it to behave this way.

While some researchers think the octopus was pushing water on the seafloor to chase prey out of their hideouts, others think it puffed up to try to scare the diver away.

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Professor Kathleen Sullivan Sealey, an associate professor of biology at the University of Miami, said the octopus pushed water down on the seafloor to find crustaceans hiding among rocks and coral

The diver and film-maker who recorded the video, PT Hirschfield, spotted the octopus off the coast of Melbourne, Australia.

On her blog, she wrote: 'While this magnificent octopus was seriously intent on finding its next morsel, I sensed that it was also becoming a tad annoyed by my continued presence.

'Whether it rushed towards me purely for having sensed some doomed crab’s movement near me which it then puffed itself up like a parachute to capture, or whether its attack posture was also intended to intimidate me remained a mystery.

'I followed as it swam and continued to film the spectacular behaviour I had never encountered before from a slightly increased distance to avoid raising its ire.'

Professor Kathleen Sullivan Sealey, an associate professor of biology at the University of Miami, told Live Science that the octopus was hunting for food.

The octopus pushed water down on the seafloor to find crustaceans hiding among rocks and coral.

'It's shooting water out of its mantle [head],' professor Sullivan Sealey said.

'It was using that water to chase little shrimp out from the rocks so that they would get caught in its legs and the webbing between its legs.'

THE OCTOPUS THAT DIES AFTER ITS PENIS DETACHES FOR MATING

The Argonaugt octopus technically has eight arms, but also has a long, detachable penis in order to mate with females that are five times as large.

Fully grown females are around eight inches long, while males can be just one inch.

They are also 600 times lighter than females.

When a female swims by, the male Argonaut sends his penis off to swim to the female and mate with her.

The penis is a ball of sperm in a tentacle called a hectocotylus that is inserted into the female's pallial cavity.

There's it's locked in so it's stored in her cavity.

In this way, females can be fertilised by more than one male by storing their 'penises' in her cavity.

The male dies soon after, but the females move one and find new mates.

Ballooning is a fairly common behaviour observed in hunting octopuses.

But researchers at the Birch Aquarium at the Scripps Institution of Oceanography at the University of California, San Diego, think the parachuting behaviour can be explained differently.

They said that in the video, the octopus changed its colour to camouflage itself to its surroundings - but when it saw the diver, it spread out its arms most likely to make itself look bigger, and also changed color.

They said it did this to make itself look big, warning potential predators not to eat it.

Then the octopus swam away and changed back to its camouflage colour.

The Scripps researchers said that the octopus was most likely a Sydney octopus, which is common in those waters.

Ms Hirschfield is an underwater photographer and film-maker who says she has a serious case of OCD - Obsessive Compulsive Diving.

She has terminal endometrial cancer and says she's swimming against it 'one scuba dive at a time.'

Scripps Institution of Oceanography researchers said the octopus puffed up to make itself look big, warning potential predators not to eat it

PT Hirschfield, the diver who took the video, is an underwater photographer and film-maker who says she has a serious case of OCD - Obsessive Compulsive Diving

Near the end of the video, the octopus torpedoes through the water, and Ms Hirschfield said that it 'hurled itself towards me like a bowling bowl and scored its intended non-impact strike.

'I quickly filled my lungs with tanked air to float a meter off the sand as it swam straight through the patch I had been resting on, directly underneath me as I tried to keep its trajectory in focus with my camera.

'I have no idea what might have happened had I not anticipated the move and acted accordingly.

'In recent times at this dive site, bold octopuses have been known to confiscate unwary divers’ cameras.'