The body of a 26-year-old swimmer who was snatched by a crocodile as he attempted to cross an Australian river has been recovered by police.

Sean Cole and a friend were swimming across the Northern Territory's Mary River when he was dragged under the water on Saturday during a birthday party.

The carcass of a crocodile that was shot by authorities following the attack was also recovered, officials said.

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Northern Territory wildlife ranger Tom Nichols said Cole's body and that of a 4.7-metre-long crocodile floated to the river surface early today. The crocodile was one of four that rangers shot in the hours after the incident.



"We believe that croc was responsible," Nichols said, though he noted that further tests to match the bite marks on Cole's body would be conducted.



The birthday part was being held at the Mary River Wilderness Retreat, an popular Outback tourist destination 70 miles southeast of the Northern Territory capital of Darwin.



Nichols said Cole, an information technology professional from Darwin, either died of chest injuries or drowned as the 650 kilogramme reptile dragged him under in a disorientating crocodile maneuver known as a death roll.



Moments after the attack, witnesses saw the crocodile swimming upstream with Cole's body still in its jaws, Nichols said.



Police Senior Constable Wade Rodgers, who coordinated the weekend search, said a report on the tragedy would be prepared for a coroner's investigation.



The river is infested with crocodiles, and officials said that as locals the men would have known that.



"They just did something silly," Nichols said.



Crocodile expert Grahame Webb, a Darwin zoologist, said he would not give a swimmer an even chance of crossing the 80-metre-wide river.



"Someone swimming in an area with crocs like that ... crocs are going to zero in on them almost every time," Webb said.