That smelly, pale yellow liquid that people flush down the toilet every day is an industrial fertilizer, a diagnostic tool, a medicine, a renewable energy resource; it is an inexhaustible substance that is produced daily in huge quantities. This is the golden story of urine.

Long massacred by whaling ships, sperm whales were almost driven to extinction. Saved when whale hunting ceased in the 1980s, the largest predators on the planet had, until then, always been studied from the surface, allowing their life beneath the seas to remain a mystery. For the first time, a team of scientific divers has literally become immersed in the day to day life of a clan.