high water mark
noun [ C usually singular ] uk/ˌhaɪ ˈwɔː.tə ˌmɑːk/ us/ˌhaɪ ˈwɑː.t̬ɚ ˌmɑːrk/
(SEA/RIVER)
（海水或河水的）高水位线
a mark that shows the highest level that the sea or river reaches at a particular place
(SUCCESSFUL POINT)
顶峰，巅峰，全盛时期
the most successful point of something
His 1991 election victory was probably the high water mark of his popularity. 他1991年成功当选很可能是他个人声望的顶峰。