A 72-year-old man threw wrenches and spark plugs to fight off circling crocodiles after his friend drowned when one of the reptiles capsized their boat.

The holidaymakers from Victoria were attempting to retrieve crab pots on Tuesday in a northern Australian creek near Darwin when a crocodile tipped over their 10-foot-long boat.

The fishermen tried to get back on board but it flipped again, trapping one of them underneath and drowning him.

The other managed to clamber on top of the boat and desperately tried to keep the reptiles away.

"He was using [wrenches] and spark plugs to hold them at bay," said Ian Badham, director of CareFlight, an Australian aeromedical charity which flew him to a Darwin hospital.

He told rescuers he got stuck in waist-deep mud as he tried to pull the boat to shore.

He managed to drag the boat to nearby mangroves where he took refuge before fellow crabbers heard his cries for help.

The dead man's body was retrieved and the survivor was found suffering from severe dehydration and exposure, Badham told the Australian Broadcasting Corporation.

Crocodiles are common in the country's tropical north and on average two people each year are killed by them.

Last month, a 19-year-old on a family camping trip had a lucky escape after he was dragged out of his tent by a crocodile which bit into his foot as he slept.

In January, a woman walking her dogs had her arm bitten off by a crocodile in a "death roll".

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