On Fri, 3 Apr 2009 19:37:33 -0600, "SteveB"
wrote:

What's the difference between a boat and a ship?

A ship can carry a boat as cargo.

That's one definition that I've heard more than once.

The international rules of the road, and some CFRs, make a distinction
at 20 meters (65 feet). Boats 20 meters long or more are classed as
"Motor Vessels" and different rules apply in some cases. The CFRs
(Code of Federal Regulations) also have different rules based on
tonnage. Ships are generally many hundreds of tons but there is no
hard and fast rule that I am aware of.