At the start of every winter, the coast of South Africa sees billions of little sardines converge in the biggest biomass migration on the planet. Alone, a sardine is insignificant and vulnerable. Together they are a formidable force that feeds an entire coastline. It is a strange decision… The sardines ride a cold current - against all odds of survival, and the purpose is largely a mystery. The shoal runs an epic gauntlet. They must pass an ancient seal colony, a lethal aerial assault by gannets and thousands of hungry sharks. But it’s when dolphins arrive that the feast really begins! Everything tips in favor of the predators, until Orcas arrive.