The Blue Planet is a British nature documentary series created and co-produced by the BBC and Discovery Channel. It premiered on 12 September 2001 in the United Kingdom. It is narrated by David Attenborough. Described as "the first ever comprehensive series on the natural history of the world's oceans", each of the eight 50-minute episodes examines a different aspect of marine life. The underwater photography included creatures and behaviour that had previously never been filmed. The series won a number of Emmy and BAFTA TV awards for its music and cinematography. The executive producer was Alastair Fothergill and the music was composed by George Fenton. Attenborough narrated this series before presenting the next in his 'Life' series of programmes, The Life of Mammals (2002), and the same production team created Planet Earth (2006). A sequel series, Blue Planet II was aired on BBC One in 2017. The series took almost five years to make, involving nearly 200 filming locations. The fact that most of the ocean environment remains a mystery presented the production team with many challenges. Besides witnessing some animal behaviours for the first time, the crew also observed some that were new to science. The producers were helped by marine scientists all over the world with state-of-the-art equipment. Blue whales – whose migration routes were previously unknown – were located by air, after some of the animals had been given temporary radio tags. The camera team spent three years on standby, using a microlight to land on the water nearby when they finally caught up with the creatures in the Gulf of California. The open ocean proved more difficult and over 400 days were spent in often unsuccessful filming trips. After six weeks, the crew chanced upon a school of spinner dolphins, which in turn led them to a shoal of tuna. Off Mexico, the behaviour of a flock of frigatebirds guided the cameramen to a group of sailfish and marlin: the fastest inhabitants of the sea. Near the coast of Natal in South Africa, the team spent two seasons attempting to film the annual sardine run, a huge congregation of predators such as sharks and dolphins, that assembles to feast on the migrating fish by corralling them into "bait balls". Meanwhile, in Monterey Bay, orca were documented attacking gray whales and killing a calf. Filming in the deep ocean required the use of special submersibles. One of them enabled the crew to dive over a mile into the San Diego trench, where the carcass of a 40-ton gray whale had been placed to attract a large variety of scavengers.