A saltwater crocodile has eaten a dog that made a mockery of it for years, to the horror of onlookers.

At Goat Island Lodge, south of Darwin in the middle of the crocodile-infested Adelaide River, guests had gathered to watch pup Pippa perform her favourite trick — running at Casey the crocodile to scare her back into the river.

But to the alarm of those looking on, including owner Kai Hansen, Pippa ran straight at her head — and Casey "did what crocs do".

The video of Pippa being dragged into the water was made worse by the screams of bystanders, but serves as a bleak warning about the river's dangers.

As Mr Hansen conceded, "it was something that had a high probability of happening sometime".

Sorry, this video has expired Terrier spends a decade taunting a crocodile

'Just doing what crocs do'

Mr Hansen came to the island 15 years ago to escape city life, living amongst a gaggle of dogs, birds and crocodiles.

While pup Hot Dog was famous for barking along to tunes on the harmonic, Pippa — also known as Dumb Blonde — quickly became known for chasing the crocodile more than 100 times her weight, with the ABC covering the dog's exploits just last year.

"You will see things that you do not believe possible," Mr Hanson had told reporters as Pippa ran at the croc in 2017.

"Take my word for it.

"It is unbelievable, this little 6-, 7-kilo dog attacks a 300-kilo crocodile."

Speaking to ABC radio this morning, Mr Hansen said he was "really sad", and had not watched the video of Pippa's demise.

But he did not think it was fair to blame the crocodile.

"She's not doing something wrong, she's just doing what crocs do," he said,

"In the early days she actually had a go at me a couple of times. These days I just throw food out from up the top and no-one is allowed to walk down there."

Casey the crocodile had been taunted by Pippa for a decade. ( ABC News: Nadia Daly )

Some on social media lashed out at Mr Hansen, saying he was to blame for encouraging the little dog to run up to the reptile.

But he said it was simply part of the dog's nature, comparing it to the dog he had as a child that would not stop chasing after cars.

"A little terrier should not do things like that. But should I stop her? I don't know, she got away with it for 10 years," he said.

Mr Hansen said he would get a new dog, and would "definitely" ensure it did not chase crocodiles.

A warning to dog owners

Crocodile expert Adam Britton agreed that the croc should not be destroyed for eating the dog.

He said it was a different situation to when crocodiles attacked humans, because that showed they learned how to attack "large prey items" and might do it again.

Crocodile expert Adam Britton said it was especially dangerous to be near crocodile-infested water with dogs. ( ABC News )

But he said the small dog was exactly the sort of prey item any crocodile would target.

"The dog got right up close to the crocodile's head," Mr Britton said.

"That basically triggers a reflex reaction, and a crocodile, if you get that close to its head, it doesn't even think about it — it will just strike.

"If a crocodile attacks a person it's a little bit different because … that can potentially lead to it getting [another] large prey item, to put it bluntly.

"So in a situation like that often the crocodile is taken out of the system.

"But a dog, at the end of the day, is not really going to make a difference to its behaviour."

He said studies from around the world showed that attacks on dogs by crocodiles, alligators, and caimans were high.

He believed the incident should come as a warning to anyone in a crocodile habitat, but particularly when they had small dogs with them.

"Going near water where there's crocodiles is a really dangerous thing to do and we always encourage people stay away from the water just in general — but if you've got a dog with you you're just compounding that risk," he said.