This is God's bathtub
It's a lake so clear, so pristine that it's been dubbed "God's bathtub".
Scientists from the University of Adelaide in Australia claim Blue Lake, on Stradbroke Island, off the South Queensland coast, appears to be in the same condition as it was 7500 years ago - untouched by climate change.
They studied the lake's water discharge and water quality and compared historical photos of the lake.
The results of study, published in the journal Freshwater Biology, were surprising.
The study's lead author, Dr Cameron Barr, told ABC Australia: "We looked at lots of different proxies of environmental change such as fossil pollen. But we also looked at fossil algae, these things called diatoms. Diatoms are very, very susceptible to changes in water chemistry.
"What we've found by looking at these diatoms, how they changed over time, is that there was very little change in the chemistry of the lake over the last 7500 years."
Dr Barr said there was no other lake like it in Australia, adding it was so clear you could see the bottom - 10 metres down. "It's like God's bathtub," he told AAP. "It is beautiful. It is absolutely beautiful."
He added that Blue Lake had been an important climate "refuge" for freshwater biota in the region.
"With appropriate management, the lake could continue relatively unchanged for hundreds, possibly thousands of years to come."
Although he wouldn't speculate on what aeffect tourists would have on the lake, Dr Barr did say Fraser Island had experienced a similar issue when people wearing sunscreen had introduced chemicals into its lakes.