a big fish in a small pond

　　someone who is important or powerful only because there are not many other people competing with them

　　(小圈子里的)大人物，小池塘中的大鱼

　　a cold fish

　　someone who is not friendly

　　冷漠无情的人

　　drink like a fish

　　To drink a lot of alcohol regularly

　　（习惯性）饮酒过度，酗酒

　　a fish out of water

　　Someone who is in a situation that they know nothing about or are not used to

　　在陌生环境不得其所的人

　　have bigger/other fish to fry

　　to have more important things to do or think about

　　还有更重要的事情要做
 
　　neither fish nor fowl

　　used for saying that you do not know what something is

　　非驴非马；不伦不类

　　There are plenty more fish in the sea.

　　Used for telling someone whose boyfriend or girlfriend has left them that they will soon have another relationship.

　　天涯何处无芳草