人山人海的英文：
[Literal Meaning]
people/mountain/people/sea
the mountain of faces and the sea of faces

[解释]
形容人聚集得非常多。

[Explanation]
huge crowds of people

[例子]
广场上人山人海，还有很多人站在高处发表演讲。

[Example]
Huge crowds of people were at the square, and many people were standing on high places delivering speeches.

[英文等价词]
hustle and bustle
multitude
vast crowd

A sea of faces
人山人海

An innumerable throng of people
人山人海

The square was aswarm with people
广场上人山人海的。

For three consecutive days, thousands of people crowded the place to see the young man painting the Buddha.
就这样，一连三天，观众人山人海，把瓦官寺挤得水泄不通。