..for most of it is covered by water. 因为这些地区大部分都被水覆盖

1. Much of our planet still remains unexplored...
   我们星球上的很多地区仍未被探索
2. ..for most of it is covered by water.
   因为这些地区大部分都被水覆盖
3. Every journey below the surface can reveal something extraordinary.
   每一次水中之旅都能揭开奇妙事物的面纱
4. More than a thousand new species are discovered here every year.
   在这里 每年有超过一千种新物种被发现
5. The ocean is home to 80% of all animal life on Planet Earth.
   海洋是地球上80%动物的家园

来自《行星地球 第三季 第二集 Planet Earth S03E02 海洋》第 2 行