The Duke of Cambridge has allowed ITV cameras to follow his environmental work over the past two years and spoke on the Norfolk coast about how rising sea levels will engulf whole communities.
He was speaking on the Sandringham estate, where both he and The Queen have a home.
The Prince warned of a "very drastic" change from rising sea levels caused by melting ice sheets.
"We’ll lose the whole lot and it’ll sweep in and stay. When sea levels rise it will stay. It will not go back out again like everyone thinks it will".
The consequences he said, in the documentary to be aired on Monday night, will be permanent.
"You’ll lose the wildlife habitats here, you’d lose the farming, you’d lose the communities.
"It’s in everyone’s interest that we protect these sorts of areas. We have to get on top of the climate change issue."
He pauses to check those with him can hear the ducks and the geese flying overhead. It is a scene many would more familiarly associate with his father, Prince Charles.
And in words that could have come from the Prince of Wales himself, William says: "You suddenly realise those extreme events are going to happen more and more in the future. And also how low lying, particularly this part of East Anglia all is."
The ITV team for the documentary, Prince William: A Planet for Us All, followed the Duke of Cambridge across the UK and Africa, filming his work alongside the veteran broadcaster Sir David Attenborough and his campaigning to stop the illegal trade in rhinoceros horn in Africa.
The Duke said: "I had to get involved because I really felt that by the time my children were 20 or 25, at the rate the poaching was at, there may not have been another rhino in the world.
"And there probably wouldn’t have been many elephants left at all."
William and Kate also talk about the threat global warming poses to all parts of the planet – not just the coastal regions.
High up in the Hindu Kush, on their royal tour to Pakistan last year, they are shown how melting glaciers will deprive whole populations of drinking water.
"If this goes wrong up here - we will lose all our water," William warned standing alongside Kate.
The Duchess of Cambridge adds: "It takes the story away from just being about the environment and climate change. It takes it into people’s homes and actually this is about water. This is about survival."
Prince William believes the younger generation will be the ones to demand more change: "I think the young are really getting it. And the younger generation are really wanting more and more people to do stuff and want more action."
William told the cameras how his eldest child, Prince George is "quite like a caged animal" and needs to get outside often and it seems William intends to pass onto him what he has inherited from his father, Prince Charles and grandfather, Prince Philip.
William said: "My grandfather, my father have been in the conservation, the environmental work for many years. My grandfather’s well ahead of his time. My father ahead of his time.
"And I really want to make sure that, in twenty years, George doesn’t turn round and say ‘are you ahead of your time?’ Because if he does, we’re too late."
Prince William: A Planet for Us All airs on ITV Monday 5 October at 9pm.