free water surface

例句：

1. 1.The free water surface is visible from the shore.
   从岸上可以看到自由水面。
2. 2. The ship was caught in a storm and drifted to the free water surface.
   船在暴风雨中被卷走，飘到了自由水面。
3. 3.The researchers found that the free water surface plays an important role in the ecosystem.
   研究人员发现，自由水面在生态系统中起着重要作用。