Tuìcháo yǐhòu, shātān shàng liúxià le hěnduō bèiké.
After the tide went out, the beach was scattered with shells.
Tips
usage
Opposite of 涨潮 (zhǎngcháo, 'high tide / tide comes in'). Famously used metaphorically in Warren Buffett's quote, often translated as 退潮的时候才知道谁在裸泳 ('only when the tide goes out do you discover who's been swimming naked').
