In the movie Titanic, how did they make the ship sink scene?

If you have seen the movie Titanic, you probably can remember when the
boat was sinking into the water. I know it was made with special
effects, but it was really amazing. The boat looked real, the ocean
looked real, and the sinking looked real. What made it more realistic
was that people were falling of the railings, and that people were
jumping off the boat. How the heck did they do it? Details please!