More than 171 trillion pieces of plastic are estimated to be floating in the world's oceans. We’ve touched on the extent of the plastic problem before on the pod, but this time we’re looking into how exactly its affecting marine creatures. Researchers say hermit crabs are increasingly using plastic waste instead of shells for shelter and they are not the only wildlife being affected by our rubbish. Our Science Correspondent, Victoria Gill, gives us a deep dive into that.

Plus, the world's largest cruise ship set sail from Miami on its maiden voyage, but there are concerns about the vessel's emissions. That’s despite the ship running on liquefied natural gas, which burns more cleanly than traditional marine fuels. So why are environmentalists worried? Jaidaa Taha, from the What in the World team, explains that for us.

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