They make up about 71% of the world's surface and are all connected. Yes, we're talking about the fascinating oceans on our planet.
But how much do you actually know about Earth's oceans? Well, we've put together 11 fiendishly tricky questions to put your knowledge to the test.
Do you have your sea legs or are you better on dry land? Take our BBC Bitesizebbc quiz to find out - best of luck!
This article was published in June 2021 and updated in July 2026
