A container filled with millions of Lego pieces fell into the sea off Cornwall in 1997. But instead of remaining at the bottom of the ocean, they are still washing up on Cornish beaches today - offering an insight into the mysterious world of oceans and tides. "Let me see if I can find a cutlass," says Tracey Williams, poking around some large rocks on Perran Sands with a stick. She doesn't manage that, but does spot a gleaming white, pristine daisy on the beach in Perranporth, Cornwall. The flower looks good for its age, seeing as it is 17...