The 75-year-old woman was snorkeling at Moore Reef some 40 kilometers (25 miles) from Cairns on Tuesday afternoon when she was "pulled unresponsive from the water", a Queensland Police spokeswoman told AFP.
Two French tourists die at Great Barrier Reef
The crew on the boat she was travelling on started CPR but she died shortly after, the spokesperson added.
The incident followed the death of a 60-year-old English tourist while diving on Agincourt Reef off the popular resort of Port Douglas last month.
Is the Australian Great Barrier Reef dead?
His death came just days after two French travelers in their 70s with pre-existing medical conditions perished snorkeling in the same area.
More than two million people visit the reef every year, generating more than Aus$2 billion (US$1.5 billion) in tourism revenues.
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