If you ever get to take a tour of The Bath Iron Works in Maine, do it. There is a superb maritime museum there, and the tour of the shipyard is fascinating.
The modular construction is very cool-they have large sections of the ship they build upside down, because they found it was much more efficient and easier for the shipworkers to bend over and work at their feet than stand on ladders with their arms over their head. They they would turn the pieces over, transport them to where there whole ship was being assembled, and attach it.
When done, they move the entire ship into this floating dry dock below, and take it out into the middle of the Kennebec river, flood it, and...voila, the ship is launched.
Now, I am a purist, and I wish they did it in the traditional fashion, sliding down the ways, but...whattaryagonnado?