A huge saltwater crocodile has charged at two workers at a reptile park north of Sydney and stolen their lawnmower.

The five-metre croc named Elvis attacked the staff at the Australian Reptile Park near Gosford after they went into its enclosure about 9:00am (AEDT) on Wednesday.

The men used their lawnmowers as a barrier when the hulking beast lunged. They escaped unharmed.

The park says the enclosure is usually tended with one mower, but this morning two were used.

The 50-year-old crocodile lost two teeth in the encounter and is now guarding one of the lawnmowers.

"Elvis is sitting at the bottom of the lagoon with the lawnmower next to him. He's guarding it," said park spokeswoman Libby Bain.

"Obviously we have to go in and retrieve the mower.

"It's not something we think he would eat but it's encroaching on his territory and he believes it is his."

Staff later distracted Elvis while the mower and his teeth were retrieved.

Elvis was acquired by the park in 2008 after it had been causing a nuisance in Darwin harbour by climbing onto fishing boats.

"He's a monster. He's the unfriendliest crocodile you would ever have the pleasure of meeting," Ms Bain said.

AAP/ABC