This week on Blue Planet II we explored the open ocean; home to some of the biggest and most spectacular creatures on earth. How much do you know about the big blue?

In 2001 BBC documentary Blue Planet broke the mould. Now 15 years later David Attenborough returns to the narrators chair as Blue Planet II re-explores the deep in stunning detail.

A planet’s opposition occurs when Earth passes ... but they don’t have to be large—any kind will do the trick,” said Kerss. “In binoculars it looks like a star, but its blueness does ...

BBC Earth's Blue Planet II explored the immense wonders of the deep. Now the team is back to celebrate marine life from all corners of the world and investigate the health of our oceans.