You're gonna need a bigger boat

Could any one tell me the meaning of the quote "You're gonna need a bigger boat" and the in what context people use this now.

It's from the movie, "Jaws." I will go google to be more precise. The sheriff character got an up close look at the shark they were pursing and said to the others on board, "You're going to need a bigger boat." The humor was in the understatement.