The red handfish (Thymichthys politus), one of the most endangered species in Australian waters. Graham Edgar

One of the most amazing things about Australia is the unique conglomeration of plants and animals that call the country’s bushlands, deserts, and coastal waters home.

But the flipside of having so many species that are found nowhere else on the planet is that once they’re gone, they’re gone. Just look at the iconic thylacine.

And while most of us are familiar with the plight of the Tasmanian Devil, stricken by deadly tumours, and the near-extinction of the elusive orange-bellied parrot, what about the creatures that are struggling for survival in the depths of our oceans?

According to Graham Edgar from the University of Tasmania, Australia has some of the world’s rarest life forms lurking just below the surface, and if we don’t pay enough attention, they could disappear before we even knew they were there.

Here are the top five Australian species that need some serious intervention before it’s too late:

5. Maugean skate (Zearaja maugeana)

A female Maugean Skate in the tannin-stained waters of Macquarie Harbour, Tasmania. Fisheries Research and Development Corporation

If this is the first time you’ve heard of this prehistoric Tasmanian ray, don’t worry – a few decades ago, even the experts didn’t know it existed.

“While doing surveys in Bathurst Harbour, I collected them in the nets, but they’re a big animal, so returned them all to the water,” says Edgar, who first discovered the species in 1988.

“I spoke to the leading skate researcher at the CSIRO, and he couldn’t place my description, so I went back and collected one.”

Turns out, what Edgar had found was one of the largest predatory species in Tasmania, which has subsequently been called the “thylacine of the sea”.

The Maugean skate is thought to exist only in the Macquarie and Bathurst Harbours of Tasmania. But even those habitats are in doubt, because there have been no confirmed sightings in Bathurst since 1989.

Sporting a large, flat body shaped like a quadrangle; a pointy snout; and a tail laced with thorns, the species is thought to have changed little from its ancestors off the ancient supercontinent of Gondwana many millions of years ago.

It’s the only skate known to permanently inhabit estuarine waters, and Edgar says this has exposed it to multiple threats in its Macquarie Harbour home – dangerously high levels of metals that trickle down from the rivers into the harbour, recreational gill net fishing, and newly-established fish farms that are reducing oxygen levels on the seafloor.

“This large Tasmanian species is on the brink of extinction, but virtually no one knows about it,” he says.

4. Red handfish (Thymichthys politus)

The red handfish (Thymichthys politus). Graham Edgar

With its bright, blood-red colouring, the red handfish easily stands out in the shallow coastal waters of eastern Tasmania, but you’ve got to find it first – and that’s no easy task.

The largest known population of red handfish boasts perhaps 10 individuals, making it one of Australia’s most at-risk – and peculiar – marine species.

“They’re red-streaked creatures with forefins used as hands, and watchful eyes,” says Edgar, adding that despite all their awkward charm, red handfish have largely been forgotten in favour of ‘high-profile’ threatened species such as the orange-bellied parrot.

And if you thought the red handfish sounds rare, that’s nothing compared to the smooth handfish, which hasn’t been seen for 200 years.

First discovered by French sailors exploring the southern Australia in 1803, the species must once have been sufficiently common to be captured with simple fishing gear, but is now known from only a single museum specimen.

Today, we simply don’t know enough about it even to say for sure if it’s extinct or not.

“If it were a bird, mammal or plant, then the disappearance of that species would be widely known,” Edgar says.

“But the issue with marine species is we don’t have enough data to say what declines are happening, and how resources should best be focused to bring them back.”

The good news is that Edgar is running a massive initiative called the Reef Life Survey, which is recruiting recreational divers to try and spot what’s left of the various handfish species.

3. Giant creeper (Campanile symbolicum)

A giant creeper snail. Graham Edgar

Large creeper snails from the family Campanilidae dominated the shallow seafloor worldwide 30 million years ago. They grew up to one metre long.

By the Nineteenth Century the consensus among naturalists was that all species had died out 10 million years ago. That was until the giant creeper was discovered in shallow waters off southwestern Australia.

“The giant creeper is the definitive living fossil,” says Professor Edgar. “It’s a species known only from rocks until the last living member of the family was discovered in patchy reef habitat near Perth.”

“Despite surviving to the present day, this mollusc is potentially heading towards extinction. Our monitoring of sites in the region indicates that recent extreme heat waves off the southwestern coast have caused populations to crash by over 80% in the past five years.

“If this population decline continues, then we may need to add creeper snails to Hawaiian honeyeaters and the thylacine, as an extinction of a whole family of animals in modern times.”

2. Brown-lined sea snake (Aipysurus tenuis)

A brown-lined seasnake on Barrow Island. Graham Edgar

Australia is known for its rather intimidating array of terrestrial snakes, but it also happens to boast the world’s highest diversity of sea snakes.

And while some species such as the venomous olive sea snake – a robust animal that swims using a paddle-like tail – occur in large numbers in Australia’s coral reefs, many others are struggling. And it’s not clear why.

Through the Reef Life Survey initiative, Edgar and his team has surveyed 200 sites around the Coral Sea and northwest coast of Australia for the first time, and they’ve documented what he describes as a “catastrophic decline” of native sea snakes.

“There is a thought-provoking boundary line across the middle of the Coral Sea,” he explains.

“Above that line, we didn’t find any sea snakes. Below that line they were common on all reefs.

“Something affects sea snake numbers north of that divide – it could be rising water temperatures and bleaching. Our volunteer crew and divers aboard a sailing catamaran allow us to survey these reefs – some 400 kilometres offshore – in way that hasn’t been done before.”

Such surveys provide hope for species such as the brown-lined sea snake, which is so little-studied that scientists don’t even have enough data to decide its level of threat.

1. Giant kelp (Macrocystis pyrifera)

Giant kelp in the Murray Channel of Chile. Graham Edgar

It’s not as charismatic as sea snakes, handfish, or prehistoric rays, but giant kelp should demand our attention based on the sheer size of the impact that will be felt if it completely disappears from our oceans.

Found around the world, the kelp forms dense underwater forests, with individual strands stretching up to 45 metres long, and growing at a rate of as much as 60 centimetres per day. This makes it the fastest-growing organism on Earth.{%recommended 6402%}

And because it prefers cooler ocean waters where temperatures remain below 21 degrees Celsius, giant kelp forests have decreased dramatically in the wake of human-caused climate change and natural warming events like El Niño – particularly in Australian waters.

As Edgar explains, that’s a massive problem, because this is not just a threatened species – it represents an entire ecological community that’s disappearing right under our noses.

“It’s the only threatened marine community officially recognised in Australia so far,” he says.

“So, it’s not only that this seaweed species has largely disappeared from Australia and Tasmania, but that a whole community of associated plants and animals is also in the process of disappearing.”