The square was a sea of people.

广场上人山人海.

《现代汉英综合大词典》

The square was a sea of people and a hubbub of voices bubbled up.

广场上人山人海,人声鼎沸.

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All you can see is a sea of people, some white and some black.

你所看到是人山人海, 有白人也有黑人.

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Corporation is a sea of people front of the traffic was also blocked.

证券公司门前简直是人山人海,把交通也阻断了.

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