The Great Barrier Reef might be the world's most famous underwater ecosystem, but hidden in UK waters lies an ancient marine world you may not have heard of. Known as maerl beds, these carpets of coral-like seaweed create some of the richest habitats in the sea. And 40 years ago, while studying one such bed for her PhD, Prof Christine Maggs found a fragment of pink-striped seaweed living on maerl she had never seen before. The discovery would become a lifelong obsession and a decades-long scientific puzzle.