The mighty Amazon River has been hiding a secret that biologists have now revealed. Beneath the muddy waters, where the river meets the Atlantic Ocean, lies a unique and massive coral reef ecosystem. It stretches across thousands of kilometres and no-one had suspected it was there. We'll find out how we missed it, how it survives, and what might threaten it in the future.

Plus - baby dinosaurs with adult proportions; and a plant that attracts ants to fend off attacks from beetles.

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