当驱逐舰搜索潜艇时，潜艇迅速下潜。

The submarine dove quickly as the destroyer searched for it.

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由连接在脚踏带上的双螺旋桨提供动力，潜艇的时速可达到8公里，并能下潜至6米深。

Powered by twin propellers connected to a pedal belt, the mini-sub can reach speeds of 8 kilometers an hour and can reach depths of 6 meters.

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那士兵使潜艇作下潜练习。

The soldier took a submarine down in a practice dive.

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