Dean Bennett, 22, told NT News how the reptile had carried out a 90-minute attack.
The crocodile had "taken chunks out of the engine" and stayed at the back of the boat until it was hit with a pole.
Dean, who was on board with his 12-year-old brother Matt and friend Ian, had anchored their boat at the mouth of South Alligator River, Northern Territory of Australia, next to another boat.
They were woken up by a loud bang, which Dean dismissed as relating to the other boat but after looking they found a crocodile at the back of theirs.
Crocodiles are known for being territorial, often attacking boat engines.
When talking about the experience, Dean said: "It (the crocodile) meant business."
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