Description Planet Earth is sometimes called "the blue planet." Do you know why? . It's because the oceans of salty water cover more than 70% of the Earth's surface, making it look blue from space. The oceans are so deep and huge that there are still many dark, distant places that are unexplored. Every year hundreds of amazing new sea creatures are being discovered by marine scientists..Focus Skills: ch, sh, wh, ph, th, compound words