Hall of Infinite Doors

You swim through the vast depths of the water, glad to note that your clothes don't seem to be holding you down. When you dive, you notice a hole and a passage leading forward. Luckily, it slopes upward, and so it's really easy for you to swim through it. You step out of the pool, and seem to exit through a similar archway elsewhere.

You're not really paying attention. The water is dripping over your eyes, and your wet clothes are making you shiver.