An enormous fifty-year-old ocean liner, the SS United States, is set to be sunk and become the world’s biggest artificial reef, off the coast of Florida in the US. The area already has over 500 artificial reefs. These are manmade structures that may mimic some of the characteristics of a natural reef. The people behind it say it’ll improve biodiversity, local tourism and fishing.

And it’s not just old ships; people have sunk oil rigs and subway carriages. They don’t always have a positive effect; in the 1970s two million tyres were dropped into the ocean to try to create an artificial reef (also off the coast of Florida), but they released lots of toxins.

Climate and science reporter Georgina Rannard explains how ships like this get turned into artificial reefs and whether old ships are good for marine life. We talk about other kinds of artificial reefs and ask what benefits they can have for our oceans.

Archive courtesy of British Pathé and CBS News.

Instagram: @bbcwhatintheworld Email: whatintheworld@bbc.co.uk WhatsApp: +44 330 12 33 22 6 Presenter: Hannah Gelbart Producers: Julia Ross-Roy and Mora Morrison Video Journalist: Baldeep Chahal Editor: Verity Wilde

East of India is a small island called North Sentinel Island. It’s home to the Sentinelese people. But no one else is welcome to visit, and if they try, they may face death. The Sentinelese have made it clear they don’t want to be contacted and prefer to be alone. But recently, a 24-year-old American tourist allegedly managed to sneak onto the island and leave a can of coke and coconut as an offering. So who are these uncontactable groups and why do people keep trying to visit?

The BBC’s global population correspondent Stephanie Hegarty tells us more about the uncontactable tribes. And Jonathan Mazower from Survival International, a charity which supports the Indigenous, tribal and uncontacted peoples, explains why social media is putting these groups in further danger.

Instagram: @bbcwhatintheworld Email: whatintheworld@bbc.co.uk WhatsApp: +44 0330 12 33 22 6 Presenter: Mimi Swaby Producers: Mora Morrison, Benita Barden and Emilia Jansson Assistant Editor: Emily Horler

The US company Colossal claim to have brought back the dire wolf from extinction after 12,000 years through genetic engineering. The three pups, called Romulus, Remus and Khaleesi, are now living in an undisclosed nature preserve, unaware that their existence has made headlines around the world. But Colossal aren’t finished yet, they want to continue to “de-extinct” other animals, such as the woolly mammoth.

BBC Science Correspondent Victoria Gill explains how the experiment was done. How realistic is “de-extinction”? And are these actually dire wolves?

Instagram: @bbcwhatintheworld Email: whatintheworld@bbc.co.uk WhatsApp: +44 0330 12 33 22 6 Presenter: William Lee Adams Producers: Josh Jenkins and Emilia Jansson Editor: Emily Horler