From Roper River, where muddy waters spill into the Gulf of Carpentaria, the barramundi run so thick they buckle nets and flood dinghies.

The afternoon before his ship was to set sail from Darwin, veteran skipper Craig 'Kooch' van Lawick was tying up loose ends - he had spent $100,000 re-fitting the boat and had forgotten the saucepan.

"It's not so much luck it's more about being prepared," he said. "We're going to sea for so long.

A whiteboard to display the weight of fish caught on the commercial barramundi fishing boat Ruby. ( ABC News: James Purtill )

"You hear the engines running now - they won't be stopped until October."

The first of February marks the start of the eight-month commercial barramundi fishing season, and this year nine boats are making the seven-day journey around the Gove Peninsula.

Kooch, 43, has been battling his wits with the metre-long silver-scaled fish since he was a 16-year-old deckhand just out of school.

"Everyone likes the idea of fishing," he said. "They think it's pina coladas and sun tans.

"It's not like that. It's dirty, long hours and isolated."

On board his vessel Ruby were a team of three other men, itinerant deckhands from New South Wales, Western Australian and South Australia thrown together by fortune.

Like nineteenth century whalers, each was chasing profit and adventure while savouring the serenity and quiet of life at sea.

But their concerns were also familiar and contemporary: one deck hand wanted to earn enough to demonstrate financial security and get his kids back, the youngest wanted to make skipper, a third was thinking of the family that was waiting for him in another state.

For the next eight months the steel-hulled boat would be their universe.

"Basically you're on a 50-foot boat that can be like a 50-foot prison cell," Kooch said.

"You've got to get your head around the fact you're living with four blokes day in day out."

'You've got to have a bit of man about yourself'

"A little bit of crazy goes good - not too much but," says Nathan Waller. "You don't want knives coming out and going to war with each other." ( ABC News: James Purtill )

Ten years ago Nathan Waller, 32, moved from NSW to WA to work the trap fishing boats out of Onslow, and headed north to the prawn trawlers and the cray boats of the Abrolhos Islands.

His dad had always said he should learn a trade, but there was plenty of work fishing and it paid well.

He took up the journeyman fisherman's life. He hopes to one day to make skipper.

"You feel safe. You always have a job in Australia as a fisherman," he said. "You rock up at any port and have a chat to the boys on the boats.

The crew's bunk beds and library below deck on the Ruby. ( ABC News: James Purtill )

"Australia is built up around the coastline. Lots of towns are coastal and pretty much anywhere you can get a job on a fishing boat."

But this apparent freedom has an important caveat: "Australia-wide everyone seems to know a bit of everyone," he said.

"If you get a bad reputation no-one wants to hire you."

As a deckhand he is paid a percentage of the take - the money the fish they catch fetches at market.

His actual percentage is a figure only he and the skipper knows.

"You don't talk wages with the other crew," he said. "Whatever you're getting paid, you're getting paid."

As a deckhand he will join the skipper and other two crew staking 500-metre-long nets in water that can be as shallow as six inches.

Typically the boat, which has a licence to use 1,000m of net, will have two of the 500m-long nets in the water, anchored end-to-end in a long line.

Bedroom, kitchen and laundry on the Ruby. ( ABC News: James Purtill )

When the nets are full they are hauled aboard and the catch sorted, filleted and frozen.

They fish the change of the tides: staking out a net, hauling it in, and then staking it out again at least every six hours.

Sometimes the net holds deadly box jellyfish.

"The boys all wear rash vests - long sleeves and that. They reckon [the jellyfish] goes straight through them sometimes," Mr Waller said.

"Stings the neck and face. I think they just tell you tough it out, sleep it off.

"I suppose you've got to have a bit of man about yourself.

"A little bit of crazy goes good - not too much but. You don't want knives coming out and going to war with each other."

'I'm not going back to carpentry ever again'

"I feel more free on the boat," says Corey Rowlett. ( ABC News: James Purtill )

Corey Rowlett, 39, got out of Perth because he hated the traffic, the driving, the congestion, and he remembered how it was fishing barramundi 13 years ago.

He had done two seasons with Kooch in his 20s and then given it up and done carpentry.

Four years ago Kooch called: he was halfway through a season and down a deckhand. Did Corey want to come up?

Corey did. He fished out that season.

"This year I gave up carpentry again to come back fishing," he said.

"I like the adrenalin, I like the remoteness, I like exploring.

"I'm not going back to carpentry ever again. I'm done running teams. I feel more free on the boat."

The sea-change is to finance a tree-change: he wants to earn enough to buy a bush block near the whaling town of Augusta in south-west Western Australia.

"I want to try and get my kids back and have a really good cruisey life," he said.

"Maybe set up another business selling fish down there."

As a deckhand earning a percentage of the take, whether he can make enough money depends on whether they can catch enough fish.

And that depends on the skipper.

"Some people have it, some people don't," he said. "Kooch is a great fishermen, one of the best I've seen.

"Some people have the knack of catching lots of fish without being able to explain it.

"He could be walking down the road and catch a fish."

'I was standing on the beach watching him get attacked'

"He had no fear of it," says Chris Wallace, remembering a crewmate attacked by a crocodile. ( ABC News: James Purtill )

Two years ago Chris Wallace, 33, was standing on a beach in north-east Arnhem Land arguing with a deckhand about swimming out to the dinghy.

It was April, part-way through the barramundi season, and they had been drinking at the yacht club in Nhulunbuy. His family were far away back in South Australia.

The deckhand dived in.

It was night-time, but it was bright enough to see the streak of white water of the crocodile.

"It came up behind him and grabbed him by the back of the head," he said.

"It rolled him over and he punched and kicked it."

The Frenchman jumped into the dinghy and motored back to the beach with blood running down his back.

"He finished the season with us. He was back in the water that night.

"He had no fear of it."

'Everything can go wrong'

"It's expensive, the rewards aren't there and we're in a fishery that could be shut down tomorrow," says Kooch. ( ABC News: James Purtill )

On the wall of the wheelhouse Kooch keeps a newspaper clipping of what happened to his last boat: struck and sunk by a bulk carrier in open water six years ago.

He had clung on for dear life waiting to be rescued.

Any time you leave port, he said, everything can go wrong.

The life of a commercial barramundi skipper, he said, was one of balancing risk and return: the riches of the ocean competing with its inherent dangers.

The 2009 newspaper showing what happened to the last boat. ( ABC News: James Purtill )

A good three-week trip can net 10 tonnes of barramundi fillet - at $25 per kilo that's worth $250,000.

"It's a great fishery," he said. "So long as we don't have any people breakdowns and boat breakdowns we'll get there. Everything has to go right," he said.

But he was also pessimistic about the future.

"It's expensive, the rewards aren't there and we're in a fishery that could be shut down tomorrow," Kooch said.

"The banks are well aware of it too. We can't go back to the bank and borrow money."

In previous seasons, he said, there had been more barramundi boats, but the industry has been in decline for the last decade.

"No doubt we'll lose some more boats out of the fishery in the next couple of years," he said.

"We've got no young guys coming up through the ranks."

Good luck tokens in the wheel house of the Ruby. ( ABC News: James Purtill )

The reason for this, he said, was not the health of the fishing grounds, but the shrinking size of the fishing zones.

"We lose area with every election," he said.

High in the wheelhouse, the skipper wears a heavy crown.

He earns the largest percentage of the take but also bears the risk and has to fund the off-season re-fit.

"Most guys that do this, their banks are pretty dry come the start of the year," Kooch said.

"We have to survive half a year with no income but of course spending money on the boat."

The Ruby carries its own diesel, petrol and water, the meat equivalent of several cows, and enough dry goods to last the season.

Every two to three weeks it will meet a barge to take on fresh provisions and deliver the fish that will end up in markets overseas and nationwide.

"To find the right people that can go out there and do that sort of job, that's the art of it," Kooch said.