The best fish swim near the bottom. 
好鱼常在水底游。  
 
Never offer to teach fish to swim. 
不要班门弄斧。  
 
Go to the sea, if you would fish well. 
不入虎穴，焉得虎子。  
 
There’s as good fish in the sea as ever came out of it. 
海里的好鱼多的是。  
 
It is a silly fish that is caught twice with the same bait. 
智者不上两次档。  
 
If water is noisy, there are no fish in it. 
咆哮的水中无鱼。（夸夸其谈者无真才实学）。