Divers found a treasure trove of Aboriginal tools on a lost chunk of the Australian continent, which sunk underwater thousands of years ago

Australia was nearly one-third bigger 12,000 years ago.

But when glaciers melted at the end of the last Ice Age, sea levels rose sharply, engulfing 770,000 square miles of the continent's coastline. Places inhabited by the Aboriginal people sunk beneath the waves, burying tools and other artifacts at sea.

Some of that lost heritage was recently found.

A study published Wednesday describes how researchers located these ancient underwater archaeological sites the first ever found in Australia and what they recovered there: 269 Aboriginal artifacts that were at least 7,000 years old and one artifact that was at least 8,500 years old.

"This discovery redrew the map of what archaeology can do on this continent," Jonathan Benjamin, an archaeologist at Flinders University and lead author of the study, told Business Insider. "We've demonstrated that if you look in the right places, you can find archaeological evidence that survived rising sea levels."

The findings offer unprecedented new insights into the lifestyle and culture of the Aboriginal people thousands of years ago. The following photos show how Benjamin's team dove down to survey and collect the underwater artifacts.

Before the seas rose, Australia's coastline extended 100 miles further than it does today. So it's likely many ancient Aboriginal sites are underwater.

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Jerem Leach

People have inhabited Australia for the last 65,000 years.

Finding those submerged sites can be challenging. It took Benjamin's team three years to pinpoint the two underwater areas where they recently found the trove of tools.

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Sam Wright

Benjamin and his colleagues decided to search an area off the Murujuga coast (also know as the Dampier Archipelago) in northwestern Australia because of its rich archaeological history. Researchers have found more than 1 million petroglyphs , also know as rock art, at inland sites in the area. Some of the petroglyphs are 40,000 years old.

"We knew there was dense cultural and archaeological landscape here, and the archipelago has lots of sheltered underwater nooks and crannies to go looking in," he said.

The team partnered with the Aboriginal people living in the area in their search.

First, they used airplanes mounted with LiDAR lasers to scan the land and sea, looking for shallow areas where potential artifacts wouldn't be covered by too much sediment or silt. Then they scanned for objects underwater using sonar-equipped boats.

Finally, the team sent divers down to investigate an area known as the Cape Bruguieres Channel in 2019.

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Sam Wright

They swam to depths of 8 feet below sea level, combing the murky sediment for signs of ancient tools.

Benjamin's students, Chelsea Wiseman and John McCarthy, were the first to find the artifacts.

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Hiro Yoshida

The 269 artifacts that Wiseman, McCarthy, Benjamin, and other team members found throughout their many dives were covered in bits of coral, sea sponges, tubeworms, and algae.

The tools weren't easy to find. "Silt turns everything same color," Benjamin said, adding, "you're just looking for shapes in the sea bed and suddenly see lithic tools pop out at you."

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Hiro Yoshida

The tools still had sharp edges, thousands of years after they'd been made and swallowed by the ocean.

The team found tools for cutting and chopping as well as stones for grinding seeds.

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Jonathan Benjamin et al./PLOS One

Using radiocarbon dating, the archaeologists estimated that the tools are at least 7,000 years old, but Benjamin said they could be far older.

At a second, nearby site called Flying Foam Passage, the divers found a freshwater spring 46 feet below sea level. In it, they found a stone tool that's at least 8,500 years old.

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Jerem Leach

Despite their varying ages and depths, Benjamin thinks the two sites could have been occupied by the same group of indigenous people.

"I wouldn't be surprised if people at the submerged fresh water spring 8,500 years ago were also over at the channel 7,000 years ago," he said.

The divers photographed and marked the location of every artifact they found but only brought a small sampling of the tools back to the surface.

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Sam Wright

"Best practice in underwater archaeology is not to disturb the site because then you lose context," Benjamin said. Researchers prefer to study artifacts "in situ," or in their original places.

The team used GPS to record the locations of the artifacts they did move. Those tools were brought back to the lab, dated, and scanned in high resolution.

Then Benjamin's team returned them to the Aboriginal community in Murujuga.

Benjamin said he was surprised at how sheltered the waters of the Diamper Archipelago were: Although a major hurricane hit the area in 2019, the artifacts didn't move.

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Sam Wright

"The straits are so sheltered that over thousands of years, there's no evidence the tools rolled, even amid stronger tides," Benjamin said.

That means that the location and distribution of the tools as the team found them is probably how Aboriginals originally left them.

This discovery gives researchers new information about what life was like for the Aboriginal people occupying Australia before the seas rose. The findings affirm that these ancient people flocked to the coast for food and resources.

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Sam Wright

"People gravitate to coastlines. If you want to know what was happening on the coasts, you have to go underwater," Benjamin said.

Without underwater research, the Aboriginal cultural record is incomplete.

"It would be like if you took the whole East Coast of the US and drew a line 50 miles in from the coast and excluded all cultural data from outside that line and then tried to tell me about America," he said.

This wasn't the first underwater archaeology in Australia: Divers and historians have uncovered multiple shipwrecks from the last century. But Benjamin sees his team's finding as unprecedented.

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Jerem Leach

"This is the first ancient indigenous site we've found that represents human occupation of dry land that was later inundated by sea-level rise," he said.

Many more submerged sites are almost certainly waiting to be found around Australia.

"The sky's the limit," Benjamin said, adding, "basically every state and territory has burning questions about its ancient past that can be looked at, if not answered, by underwater archaeology."