It is a scene that had BBC viewers on the edge of their seats, as freshly hatched sea iguanas were picked off one by one by a knot of vigilant snakes as they attempted to race to safe ground.
Now, behind the scenes footage from the first episode of Planet Earth II shows an up-close look at the gripping events that have since been labelled 'the stuff of nightmares,' revealing the gruesome fate of hatchlings who didn't manage to escape.
According to the crew, this behaviour has never been caught on film before - and as the snakes swarmed in from all sides to hunt, a cameraman knelt just feet away.
In the footage, BBC cameraman Richard Wollocombe can be seen filming the moment a hatchling marine iguana dashes for its life just after emerging from the sand on Fernandina Island in the Galapagos.
Within seconds, racer snakes appear from every direction and pluck the baby iguana from the rocks, descending upon it in a constricting tangle.
"This is the first time snakes have been filmed hunting en masse," the BBC reveals in the new footage.
But, don't be fooled by what appears to be a cooperative tactic.
Just one snake may be lucky enough to capture its fast-moving meal, and the predators will even eat each other amid the chaos.
In the footage, one of these snakes can be seen swallowing both a successful hunter and its partially eaten meal.
"They aren't working together," the BBC explains. "It's every snake for itself."
In the original footage, hatchlings could be seen emerging from the sand of the Galápagos island in the Pacific Ocean in June for what is the snakes' best feeding opportunity of the year, and most were lucky enough to escape.
The footage on BBC1 showed some iguanas outrun the snakes to safety by the sea while others were caught before the snakes wrapped themselves around them.
When the crew saw the snakes for the first time, they were too shocked to film - and host Sir David Attenborough had never seen anything like it either, it was claimed.
Among the millions of viewers captivated by the footage was Olympic rower Will Satch, who described it as a 'real life horror film'.
He tweeted: "Bloody snakes chasing those poor sea swimming iguanas. David Attenborough is exactly what this world needs and plenty of him."
Sir David's commentary told how the snakes' eyes are poor, but they can detect movement and are on alert for other iguanas after seeing one.
Viewer Alex Barreto praised the "absolutely disgusting but incredible footage", while Claire Macmillan expected to have "nightmares about those racer snakes".
And Reece Caddick said: "I will 100 per cent have nightmares about those snakes on Planet Earth. Never thought I would be emotionally attached to an iguana."
Meanwhile ITN lighting cameraman Matt Freestone hailed the sequence as "probably the most brilliantly edited piece of television I've seen in ten years".
The hotly-anticipated series, which is formed of six parts and follows on from the first Planet Earth in 2006, has taken three years of filming and 117 filming trips.
The first episode focused on island life and used nine filming locations. Next week the show will look at mountain animals including a rare sighting of snow leopards.
TV critic Jim Shelley said: "One chase scene and narrow escape was more thrilling than anything in James Bond and actually not that different."
He added that the racer snakes "sounded scarier and scary enough without the sight of them hunting in packs, like a scene from Indiana Jones."
And Daily Mail TV critic Christopher Stevens, who gave the first episode of the new series five stars, described last night's sequence as 'truly edge-of-the-seat'.
He said the predators writhed together "like a mythical animal with a dozen heads" and "they looked like animated clay monsters from an old-fashioned horror movie".