Prince William says world leaders need to 'act urgently' to save our oceans

Prince William has urged world leaders to "act together with urgency" in order to protect the planet's oceans.

He delivered a speech on Sunday saying how important oceans are for our environment and that more money needs to be spent to preserve them.

The prince was speaking in Monaco at a special event ahead of the United Nations (UN) Oceans Conference in Nice, .

It's a big event where countries come together to talk about how best to protect our oceans.

The last one happened three years ago, and the aim this time is to get 60 countries to approve something called the High Seas Treaty.

If they do, it would give 30% of the seas around the world protected status to stop overfishing and other damaging practices.

The conference, which is happening all week, will also look at the role oceans play in global trade, food security and sustainable energy.

Speaking to an audience of environmentalists, scientists and investors, Prince William said life on the ocean floor was "diminishing before our eyes" and called for ambitious action "on a global, national and local level".

He said he understood the sea can feel "distant" to many at times, but that we shouldn't underestimate its importance: "For many, it is an urgent wake-up call to just what is going on in our oceans. But it can no longer be a matter of 'out of sight, out of mind'.

"The truth is that healthy oceans are essential to all life on earth. They generate half of the world's oxygen, regulate our climate and provide food for more than three billion people," he said.

He ended his speech by quoting Sir David Attenborough: "If we save the sea, we save our world."

Oceans are a vital part of the planet's ecosystem - especially since they cover 70% of the surface of it.

They produce over half the world's oxygen we need to breathe, and absorb tonnes of carbon dioxide, the planet-warming greenhouse gas.

Millions of different species live in the sea, which are, among other things, crucial for many people's diets around the world.

And they're a huge source of renewable energy, as the motion waves they make can be turned into electricity.

Ahead of the Oceans Conference, Buckingham Palace released a video of Prince William chatting with environmental legend Sir David Attenborough.

David Attenborough has recently released a film called Oceans, in which he states how important it is that people look after them.

When speaking to the prince, Sir David said he hopes the leaders gathering for the UN conference will "realise how much the oceans matter to all of us, the citizens of the world".