Definition: the ground under a river, lake, or sea Level: B1
我们在湖底看到了一个多样化的生态系统。
We saw a diverse ecosystem at the ___bottom of the lake.
残骸静静地躺在海底。
The wreck rests on the ___bottom of the sea.
河底的石头很光滑。
The stones are smooth on the ___bottom of the river.
