I learn his joke from a movie called 

Philadelphia (1993) 

Q:What do you call a thousand lawyers chained together at the bottom of the ocean?

A: A good start.

but I still can not understand what does this answer mean ,so I google it ,find some explain below :

http://www.psychprogram.com/Claims/defense.htm

Lawyer jokes have been around as long as there have been lawyers, and most of us (this writer included) can admit to telling a few. Although we can all use a good laugh, there’s a time when lawyer jokes aren’t so funny: the unfortunate time of facing a possible malpractice suit.

That’s when we learn to love a lawyer. However, you need to know about your legal defense team before facing a potential suit. That is truly “a good start.”

but I stiil can not get the point,who can tell me?