That was filmed before 2016, when the first of back-to-back mass bleaching events hammered the world's largest living organism, killing about half the shallow-reef corals of the Great Barrier Reef.

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John Rumney, director of Great Barrier Reef Legacy, was on board for the filming of the BBC documentary. During the recent visit to the damaged site, he noted that two years on, there are "very few signs of recovery" and "almost no visible recruits" from coral spawning.

"In a healthy reef system, where we would not have any more impacts including cyclones, crown of thorns starfish, and further bleaching impact, this site would take between 10 and 15 years to fully recover," Rumney says.

Frequency of bleaching on the rise

The likelihood of the Great Barrier Reef - or other tropical reefs around the world - having that time to rebound is fast disappearing.

As Terry Hughes and other researchers at James Cook University stated in a peer-reviewed study earlier this year, the frequency of severe coral bleaching events has increased fivefold in just four decades because of global warming.

When ocean temperatures exceed certain thresholds, heat-stressed corals expel tiny zooxanthellae algae that provide most of their energy and vivid colour. Some will recover but others die or have reduced growth.

Tourism shifts

It's a realisation that's sinking in, even among tour operators who initially threw their publicity efforts into trying to deny the reef has a problem.

The Association of Marine Park Tourism Operators (AMPTO) in May co-drafted a statement with the Australian Marine Conservation Society that finally puts climate change at the forefront of threats to the reef.

"The federal government has a responsibility to honour the Paris [climate] agreement and to protect the Reef on behalf of all Australians, all humanity and future generations," according to a statement that groups are still gathering signatures for, prior to its formal release.

"Yet our representatives continue to support the expansion of coal and gas, including Adani’s mega coal mine," it said. "To give our Reef the best chance for the future, Australia must join the rest of the world to rapidly phase out coal and other fossil fuels and transition to renewable energy."

Col McKenzie, AMPTO's chief executive, says it is time "to take a more public stance" on climate change.

“It was the bleaching events in 2016-17 that drove the message home," he says, adding reluctance within his 11-member board - particularly from tour operators who refused to accept man-made climate change - had restricted his ability to speak out in the past.

Those climate change deniers have largely gone quiet, he says, with typical bluntness: "They realise it’s bullshit and we can’t be continuing it."

'Environment is our economy'

To local government leaders such as Julia Leu, mayor of Douglas Shire, the shift in AMPTO's position is to be welcomed.

"There has been a change because of increasing awareness in the community," Leu says. "I’m really pleased."

Leu says Far North Queensland can be a lonely place for environmentalists but the realisation so much of the economy depends on the Reef - estimated to be worth more than $6.5 billion a year to the Queensland economy, and employing 64,000 people - can't be ignored.

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“The environment is our economy," she says. Along with the World Heritage-listed Wet Tropics, the Reef is responsible for as much as 80 per cent of economic activity in Douglas Shire, drawing 110,000 international visitors each year.

According to the first scientific assessment of the threat of bleaching to the world's 29 World Heritage-listed reefs published last year by UNESCO,  business-as-usual emissions of greenhouse gases would result in mass bleaching for the Great Barrier twice a decade by 2035 and annually by 2044.

A trajectory of emissions peaking by 2040 and then declining - more closely in line with the Paris climate goal of keeping global warming to less than 2 degrees compared with pre-industrial times - would only delay annual bouts of severe stress to 2051.

Restricting warming to 1.5 degrees would spare all but four of the 29 reefs - including the Great Barrier Reef - of those frequent bleaching events, according to an update published last month.

'Gut-wrenching'

While the tourism body is finally speaking out about climate change, individual operators are not always welcoming the discussion of bleaching.

"Some actually sack staff if they mention climate change," says Charlie Veron, a marine biologist dubbed "the Godfather of Coral" for describing about a quarter of the world's corals and running the Corals of the World website.

Veron describes as "gut-wrenching" his feelings of seeing so much of the reef lost: “It’s like watching my house slowly burning down."

"There’s a lack of appreciation of how serious it is," Veron says. "There’s not going to be any jobs, there will be no tourism" if the reef is allowed to die.

'Most amazing job'

Tanya Murphy, a Cairns-based diving instructor, is prepared to put up a fight. Her group, Divers for Reef Conservation, has led some of the local opposition to Adani's proposed Carmichael coal mine in Queensland's Galilee Basin.

Visitors are, of course, taken to the most intact parts of the reef, where they can see the most colourful corals and even Nemo-type clownfish.

"Every day, I see turtles and hundreds of fish and corals, and tourists continually tell me that it is one of the best experiences of their life," Murphy says. "They’re still loving it - it’s really great for us."

Tourism numbers recovered from a dip soon after the coral bleaching events first become public and are running at record levels, according to the Great Barrier Reef Marine Park Authority.

"It's important that people continue to enjoy and love the reef and don't give up on it, because although it's struggling, it's not too late to save it," she says, adding that phasing out fossil fuels and switching to 100 per cent renewables would be a start.

“I want to keep working on the reef for the rest of my life," Murphy, 32, says. “It’s the most amazing job in the world and I’d never give it up.”

The author travelled to the Great Barrier Reef courtesy of the Climate Council.