Big Al's health takes a hit while searching for new ground.

Yogi risks a showdown with the law as he heads into South Australia, and Steve is under pressure with a truck down and a run to a place he's never been to.

Jacqui and Andrew unearth the biggest nugget of their careers, the Ferals invest in a mobile sluice that could save their season, and the Poseidon Crew struggle with a waterlogged lease.

The Poseidon Crew clash over a risky return to the Slip Up lease, Shane and Russell suffer another mechanical breakdown, and heat and exhaustion puts the Ferals' hopes of reaching target in jeopardy.

Record cattle prices and a wet season have turned the outback into a gold mine for bull catchers; husband-and-wife team Liz and Willie Cook are expanding their empire, but with ever-increasing debt.

Mike and Connor argue about restoring a 1967 Chevy II to original factory condition or as a high end 'resto-mod' with 21st-century touches, and a drag race brings out everyone's competitive spirit.

A rescue team races to save a seal pup and an ailing sea lion as scientists hunt what's killing the coast's vanishing grey whales.

We take a look at the most incredible metropolitan railways, from an inverted monorail in Wuppertal German to London's ground-breaking Crossrail project and a freight system that supplies New York.

Andrew and Jeff discover a hidden cave in search of clues and an unexpected find that injects the team with fresh hope.

Shane and Russell rebuild a wet plant in a bid to rescue their season, the Victoria Diggers are forced to dig a neighbour's lease, and brothers Marcus and Linden are stranded in the Outback.

The Poseidon Crew hit the jackpot after being forced to detect just to survive, the Goldtimers' rookie season goes from bad to worse, and the Dust Devils unearth a million-dollar reef.

Chris and Nika's best start ever may be blown by a good deal gone bad.

Norman has dreamt of owning a Volvo 850R since watching Volvo British touring cars race, but fixers Sheldon and Peter could struggle to bring Norman's dream to life.

Disaster strikes when a would-be thief crashes the Desert Diggers' loader; Shane and Rusty drag their dry blower across treacherous ground; Jacqui and Andrew recruit a new prospector to their team.

A mechanical failure puts Brent's son Cayden to the test, a fuel theft grinds the Mackies' operation to a halt, and the Wanderers race to secure a crucial gold deal before a week's end.

The heaviest rainfall in 70 years sparks flooding in NSW; in Queensland, diver Mackie puts his life on the line in the murky Mary River so that Clayton's Towing can undertake a land-to-water tow.

Crane operators load millions of pounds of timber in a cold snap, a halibut fisher chases quota, and a diver visits a wolf eel.

Ken and Guillaume race to get sluicing before Ken leaves for the birth of his son.

Marcus, Linden and Dale desperately need new ground, the Poseidon Crew's hope for a 1000-ounce nugget is slipping through their fingers, and Shane and Russell take the biggest gamble of the season.

Heavy rains in Victoria threaten to shut down the Poseidon Crew, Jacqui and Andrew struggle through 40°C heat in Queensland, and the Goldtimers negotiate a lucrative deal to sell their mining rights.

Irv imports an original-run short wheelbase Porsche 911 from the East coast of America. He needs to make it roadworthy while keeping its incredible sun-faded patina.

In France and Italy, engineers battle crushing rock pressure, unstable geology and extreme underground conditions to build the longest railway tunnel ever constructed beneath the Alps.

With porn consumption at an all-time high, more people than ever are looking to turn clicks into cash; Olivia delves into its world.

Paul and the SOS team take on a mining mystery as they try to find and fix the causes of a two-year dry streak that threatens to end the prospecting dreams of rookie miners Chris and Vince.

The Victoria Diggers may have stumbled on a million-dollar motherlode, the Scrappers are at breaking point, and Dirt Dog Jake and his new recruits are urgently trying to supersize their operation.

History is made as one team unearths the biggest gold nugget ever found by the Aussie Gold Hunters; the Gold Gypsies get their excavator back from repairs; Greg and Chris hit a patch of gold nuggets.