When we broke camp in the morning it seemed as if the entire land was covered with the animals. They were in such throngs that the sound of their hoofs was like the rumbling of distant thunder. ​
​One could compare the scene to nothing more than to an ocean of dark water surrounding us on every side. pitching and tossing as if under the influence of a strong wind.
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Which statement best describes what the underlined metaphor in the sentence adds to the meaning of the text?