a line or mark showing the highest point that the sea or floodwater has reached 高水位线（海水或洪水所达到的最高水位） We pulled the boat up the beach above the high-water mark. 我们把船拉到高水位线上的海滩上。 - (figurative)
the high-water mark of Parisian fashion (= the most successful time) 巴黎时装最流行的时期