这些海的海底是中国东部大陆在海下的延伸。

The floors of these seas are extensions of china's Eastern mainland submerged in the water.

youdao

海和海下的十二只牛。

One sea, and twelve oxen under it.

youdao

飞行器利用机翼上下两面的压力差形成提升力以平稳的在空中飞行，而潜艇在原理上形同海下的热气球，通过调节自身浮力或升或降。

Aircraft use lift from their wings to stay aloft, while submarines operate like underwater balloons, adjusting their buoyancy to sink or rise.

youdao