David Attenborough narrates a natural history of the oceans. This edition explores a force so powerful that it moves oceans - the tides. All over the world tides create opportunities for marine life: giant sting rays glide on currents for a rest, the fastest snail of all surfs waves in pursuit of dinner, minute crabs play football on the beach, racoons binge and, in a unique sequence, dolphins play a deadly game of catch. For in the ocean, each turn of the tide spells life or death, somewhere.