Keegan Payne, 19, was the one who reeled in the million-dollar fish but it was his little sister who spotted a small tag on the barramundi which led to a "life-changing" jackpot.
The small rod of red plastic clipped to the spine of the barra meant Keegan landed top prize in the Northern Territory's annual Million Dollar Fish competition.
Keegan, who works two jobs and lives with his family of eight in Kimberley, said he plans to treat his family to an overseas holiday and stash the rest in the bank.
Speaking on 2GB, the keen fisherman said he'd woken up feeling "pretty good" about his sudden change of fortune.
"It's life-changing for us," he said.
Keegan said his family celebrated by staying at a hotel last night, while he escaped from doing media interviews and went fishing instead.
Reflecting on how he became an instant millionaire, Keegan said his line was only in the Katherine River for a "couple of minutes" before the barra bit.
"We were chucking out yabby pots ... and we caught a cherabin (freshwater prawn) in the pot and we chucked it on for a bit of live bait," he said.
"We waited a couple of minutes and the line started pulling."
Addyson, 11, was on the boat with Keegan and his friends and she had pointed out the unusual red thing sticking out from the 67-centimetre fish.
Keegan agreed he was lucky Addyson had spotted the tag, but was non-committal over whether she'd be getting a slice of the prize.
He called the phone number on the tag and was told he needed to keep the fish alive.
They nearly crashed the boat racing back to the boat ramp, he said.
Each year, competition organisers release more than 100 fish with red tags in Darwin, Katherine, Arnhem Land, Kakadu and Tiwi Islands waterways.
Some are worth $1 million while the rest are worth $10,000.
The competition has been running since 2015 but nobody had landed a million-dollar fish until Keegan struck it lucky.
Have you recently caught a fish of note around Australia? Send a picture of your catch and a few words describing its capture to smarsh@nine.com.au.
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