A three-metre-long crocodile was being fed by an Adelaide River jumping crocodile cruise when another croc, known as Dominator, snuck up behind it.
The tussle took place largely underwater before Dominator re-emerged from the water with the other croc's leg in his mouth.
It was quite the show and shock for those on the boat.
However, it's not the first time Dominator has eaten one of his own in front of shocked tourists.
The territory's largest and most infamous reptile, who is believed to be more than 80 years old, was seen biting and thrashing a juvenile croc within metres of another boat on the Adelaide River near Darwin in May last year.