【英文什錦菜 】一流

first water 一流 

中英文一字不差

https://www.collinsdictionary.com/dictionary/english/first-water

1. 

the finest quality of diamond or other precious stone

2. 

the highest grade or best quality

3. 

the most extreme kind

a fool of the first water

 

https://en.wikipedia.org/wiki/First_water

 

In the gemstone trade, first water means "highest quality

 

比first class 還牛

學校教學設施先進，辦學條件一流。
School teaching advanced facilities, first-class conditions for running schools.