There are 320 million cubic miles of water on Earth and that is all we're ever going to get. The system is closed: practically speaking, nothing can be added or subtracted. The water you drink has been around doing its job since the Earth was young. By 3.8 billion years ago, the oceans had (at least more or less) achieved their present volumes.
地球上有13亿立方公里水，这是全部。系统已经关闭，说得明白一点，再也不会增加，再也不会减少。你喝的水，自地球形成之初起就在这里忙碌。38亿年以前，海洋（至少大体上）已经达到现在的规模。

The water realm is known as the hydrosphere and it is overwhelmingly oceanic. Ninety-seven percent of all the water on Earth is in the seas, the greater part of it in the Pacific, which covers half the planet and is bigger than all the landmasses put together. Altogether the Pacific holds just over half of all the ocean water (51.6 percent to be precise); the Atlantic has 23.6 percent and the Indian Ocean 21.2 percent, leaving just 3.6 percent to be accounted for by all the other seas. The average depth of the ocean is 2.4 miles, with the Pacific on average about a thousand feet deeper than the Atlantic and Indian Oceans. Altogether 60 percent of the planet's surface is ocean more than a mile deep. As Philip Ball notes, we would better call our planet not Earth but Water.
水域被称之为水圈，它的绝大部分是海洋。地球上97%的水都在海里，太平洋占了较大部分。太平洋的面积比所有的陆块加起来还大。总的来说，太平洋占所有海水的一半以上（51.6%），大西洋占23.6%，印度洋占21.2%，其他所有的海祥加起来只占3.6%。海洋的平均深度为3.86公里，太平洋平均要比大西洋和印度样深大约300米。这颗行星60%的表面都是深度在1.6公里以上的海洋。莫利普·鲍尔指出，我们这颗行星不该叫做地球，而该叫做水球。
Of the 3 percent of Earth's water that is fresh, most exists as ice sheets. Only the tiniest amount—0.036 percent—is found in lakes, rivers, and reservoirs, and an even smaller part— just 0.001 percent—exists in clouds or as vapor.
地球上只有3%的水是淡水，主要以冰原的形式存在。只有一丁点儿淡水——0.036%——存在于湖泊、河流和水库之中，更小的一部分——只有0.001%——存在于云团，或以水蒸气的形式存在。