My explanation might seem a bit difficult to grasp if you're not familiar with Buddhism, not that I'm an expert or anything. At first I wasn't sure why there was a door inside the temple dividing the sleeping quarters from the rest of the place. I watched the film in my Korean & Japanese Religions class. The class was great, and one day while on the internet, I read about a collection of koans (paradoxical riddles, questions, dialogues meant to stop logical, one-way thinking and spark enlightenment) called "The Gateless Gate." The gate is gateless because we've already passed through it; we are already all Buddhas in Mahayana Buddhism but we just don't know it. Then I realized that there was no real purpose for having a door with no wall present; one could easily circumvent (correct word?) the door or gates, just like one can easily walk through a gate that is gateless. So, I think that the door in the temple and even the gates that divide the water from the land are there to urge us to tap into our "Buddha nature" and realize that nothing separates us from it. In general, no two things are separate from each other in the Law of Dependent Origination. So, in a sense, the presence of gates and doors in the movie is almost humorous, if this analysis is correct.
Anyway, I hope that explanation makes some sense. My professor agreed with it. It was just sheer luck that I stumbled across the title "The Gateless Gate" and something clicked.
I want to buy the film on dvd because I'm dissatisfied with the downloadable versions which have no subtitles! haha