A 39-year-old man has died after being attacked by a shark on Sunday while fishing on the Great Barrier Reef, police said, the second fatal shark attack in Australia this month.

The man was one of four people who took a seven-metre-long boat to Kennedy Shoal, a shallow reef around 45 km (28 miles) off the coast of the state of Queensland in northeast Australia, Queensland Police Service Inspector Elaine Burns told reporters.

“We believe the man had been spearfishing when he was attacked and died from a critical head injury,” she said. “He was retrieved from the water by another person who was in the water with him at the time of the attack.”

It took the boat more than an hour to reach the shore after calling the emergency services, Burns said.

“He was declared deceased at the boat ramp.”

The police did not identify the man. Burns said it was not yet clear what type of shark had assaulted him and added that no one else was injured in the attack.

The death follows that of a 38-year-old mauled off an island near Perth in Western Australia on May 16.

There are around 20 shark attacks in Australia every year but the vast majority are not fatal, according to data from conservation groups. Far more people drown on the country’s beaches.

Dozens of beaches along Australia’s east coast, including in Sydney, were closed in January after four shark attacks in two days. Those attacks came after heavy rain created murky water that attracts sharks and reduces their visibility.