Researchers said in a study published on Wednesday they had found the first underwater Aboriginal archaeological sites off the coast of north-western Australia.

The Aboriginal artifacts were discovered during surveys at Cape Bruguieres and Flying Foam Passage in the Dampier Archipelago, a group of 42 islands off Pilbara in Western Australia.

The finds date back thousands of years to a time when the current seabed was on dry land, the international team of archaeologists said in the study published in the journal Plos One.

The two underwater sites provided new evidence of Aboriginal life and yielded hundreds of stone tools, including grinding stones, researchers said.

"These new discoveries are a first step toward exploring the last real frontier of Australian archaeology," said lead author Jonathan Benjamin, an associate professor at Flinders University.

More than 30% of Australia's landmass disappeared underwater as seas rose following the last ice age, some 2.6 million years ago.

"This means that a huge amount of archaeological evidence documenting the lives of Aboriginal people is now underwater," Benjamin said. "Now we finally have the first proof that at least some of this archaeological evidence survived the process of sea-level rise."

Some 269 artifacts were mapped at Cape Bruguieres about 2.4 meters (7.8 feet) below modern sea level, researchers said, while the radiocarbon dating and analysis showed "the site is at least 7,000 years old."

At the second site, estimated to be at least 8,500 years old, located at the Flying Foam Passage, researchers found an underwater freshwater spring.