The flood and ebb tides alternates with each other.

涨潮和落潮交替更迭。

《新英汉大辞典》

Flood and ebb, it's about timing: Tide is a phenomenon of regular rising and falling of sea level mainly influenced by the gravitation of sun and moon.

涨潮退潮，掌握时机：潮汐是一种有规律的海面升降现象，主要是受太阳与月亮引力的影响。

youdao

The Jiaozhou bay is a tidal inlet of bedrock bay type, the typical flood and ebb tidal deltas are developed inside and outside the bay mouth, and the geomorphologic system in the bay is complete.

胶州湾属基岩海湾型潮汐通道，湾口内、外发育较为典型的涨、落潮流三角洲，地貌体系较为完整。

youdao

As the tide rises, a flood-tidal current moves in one direction and as the tide falls, the ebb-tidal current moves in the opposite direction.

UNESCO: L O S S A R Y