Prince William has warned the world's oceans are "diminishing before our eyes" and called on the world to "think big" on how to revive them.
Speaking at the Blue Economy and Finance Forum in Monaco on Sunday, he said everyone is responsible for change - both negative and positive.
"What once seemed an abundant resource is diminishing before our eyes," he said.
"We all stand to be impacted."
It comes as he teamed up with Sir David Attenborough in a social media video to talk about the harmful effects of over-fishing, pollution and temperature rise on our marine environment.
"This challenge is like none that we have faced before," the royal continued.
"But I remain an optimist. I believe that urgency and optimism have the power to bring about the action needed to change the course of history."
The Prince of Wales is also the founder and president of the Earthshot Prize, a global award that celebrates environmental initiatives. Finalists for this year's award were due to attend the event.
He ended his speech with a call to action intended to go further than just Monaco or even Europe.
"Halfway through this decisive decade, I call on all of you to think big in your actions.
"Let us act together with urgency and optimism while we still have the chance.
"For the future of our planet. For the future generations. We must listen to the words of Sir David Attenborough: 'If we save the sea, we save our world'."
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To coincide with the event, and to attract a greater audience, a YouTube video was posted by Kensington Palace, showing William and Sir David Attenborough laughing together as Sir David tried on his first-ever diving helmet.
But their conversation soon turned to more serious matters when they discussed Sir David's new film, Oceans, and the horrific examples of damage uncovered.
(c) Sky News 2025: Prince William warns world's oceans are 'diminishing before our eyes' in call for urgent action
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