Michael Newman was kicked out of a pub in Broome for being too drunk and went on to scale the fence of an enclosure, before trying to sit on the 800kg saltwater crocodile.
BBC News reports that Fatso the crocodile bit the 36-year-old man's leg, tearing chunks of flesh from him as he straddled the reptile.
Heavily injured, Newman then staggered back to the pub where the manager, Mark Phillips, described seeing him with bits of flesh gouged.
Phillips told The West Australian: "They said he had chunks out of his legs and things like that."
Newman received surgery to serious wounds to his leg and is recovering in hospital, according to police.
Malcolm Douglas, the park's owner, said that the crocodile was capable of much more than the injuries Newman sustained.
"If it had been warmer and Fatso was more alert, we would have been dealing with a fatality," he said.
An average of two people are killed each year in Australia by aggressive saltwater crocodiles, which can grow up to 7m long and weigh more than a tonne.
> Crocodile found in bath, man faces jail