An official says a 72-year-old man told rescuers he threw spanners and spark plugs to keep crocodiles at bay after a croc capsized his boat in a northern Australian creek and his friend drowned.

Rescue helicopter director Ian Badham says the two tourists from the southern city of Bendigo were attempting to retrieve crab pots on Tuesday when a crocodile nudged their 3-meter (10-foot) boat and tipped it over at Leaders Creek, southwest of Darwin.

The drowned man, aged in his 50s, became trapped under the boat while the survivor scrambled upon the upturned hull.

The survivor was rescued by professional crabbers three hours later.

Badham says the survivor was treated for shock before he was flown to a Darwin hospital. He was later discharged.