Drinks like a fish 

Someone who drinks a lot

John smokes like a chimney and drinks like a fish.

Drinks like a fish by mrWAB February 9, 2015

drink like a fish 

to drink to excess

He was unaware of the danger that could come to him if he were to drink like a fish and as a result he almost succumbed to alcohol poisoning.

drink like a fish by The Return of Light Joker April 3, 2009