transporting a sailboat via container ship
Faith, there are several shipping companies which offer well-dock service; Dockwise is the largest and transports boats all over the world using a relatively large fleet of well-dock ships. http://www.dockwise.com/
This can be costly tho'' costs can be less if you catch the ship on its ''deadhead'' run e.g. when the ship is leaving a U.S. port for the Med in the Fall, when there''s more demand for vessels to be heading for the Caribbean *from* the Med than vice versa.
Aside from well-dock service, there are many companies which are willing to sling you aboard as deck cargo. This requires a cradle for your vessel to sit in, and the safety of your boat is dependent on the weather conditions experienced by the ship, soundness of the tie-down, degree of theft present on the boat, etc. It''s all these variables - and the effort it takes to track down a ship willing to provide this service - that makes the well-dock companies so inviting.