Why end on a boat?

This movie was so messed up you could basically come up with any number of crazy explainations as to why it ends on a boat. I believe it sums up the feeling of the story. The characters seem to be just wandering the earth with no steady direction or destination (like a ship). They seem to be floationg through their existence, swaying back and forth with every turn of the plot (like a ship). They seem to be at the mercy of other factors in the story, never determining their own course (like a ship).

The ship is symbolic of their lives as they relate to the story.