If you go high up into the air and look at the Earth, the colour you will see most is blue. There is water on 361 million square kilometres of our plant – that is more than 70 % of the Earth. In many places the world’s oceans are 5,000 metres deep. The deepest part of the ocean is the Mariana Trench, east of the Philippines, Which goes down for 10.9 kilometres. In the warmest places, the water in the oceans can be 26 ℃ but in the icy waters near Antarctica it can be as cold as – 1.4 ℃. And there are hundreds of different species in the sea, from very little ones up to the blue whale, Which can grow to twenty-six metres long.