Do you mean fishing tables?

 

Fishing towers aren't usually "towers," but they are essentially a contraption (bad word for it) of water ending at thinnest point on signs, a certain number of blocks above the user. They don't require any aiming and work every catch.

How to make 'em, though.. Best ask someone in-game if you can look at their tower. I don't know how to explain how to place the blocks. xP

 

Think about a hollow tower. Then water at the top with signs below to keep it from falling. You throw your rod up and it will only come down when the fish gets caught.