Marine biologist, diver and author Dr Helen Scales takes Dr Karl deep beneath the waves to share her passion for the ocean. Helen talks about the secret life of molluscs (shellfish). Hear about 'clacking' oysters, the legend of the Golden Fleece (sea silk) and a creature resembling a pinecone crossbred with a slug. There's maths in the spirals, slave trading in the cowrie and just imagine a Harry Potter golden snitch of the sea… it's real and plays an incredibly important role.