Why is the Earth called "the blue planet"?

The Earth is referred to as "the blue planet" because of the abundance of water on the planet. Over 70 percent of the Earth's surface is comprised of water, producing a vivid blue color when viewed from space.

The Earth's oceans contain about 1.3 billion cubic kilometers of space, which is 95 percent of all habitable area on the planet. In addition to covering most of the Earth's surface area, the oceans provide a habitat to somewhere between 700,000 and 1 million species. Many barriers to exploring the oceans still exist, and as many as two-thirds of marine species have yet to be identified. This makes the oceans one of the last remaining unexplored frontiers of science.