The flood and ebb tides alternates with each other.

涨潮和落潮交替更迭。

《新英汉大辞典》

And Mr Rush's grandfather-perhaps the most influential of all, for the flavour of this man of the sea runs throughout the book as certainly as the ebb and flood of the tides.

还有他的祖父——也许是所有人中影响他最深的一个人，因为他对这个属于海洋的男人的喜爱始终贯穿于全书，这一点就像潮水的涨退一样确信不疑。

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