Man are my cheeks sore - NEMO Spoilers ahead

[Sub la Goon]

From what I can tell:

Spoiler:

The subs are always in water but when you go through the show scenes, you are looking through the water outside your porthole and then another piece of glass in front of the scenes themselves. You don't see the building glass because it is so close to you and the seams are integrated so well. So, it's kind of like being in a flume ride but looking out from beneath the water's surface and through a clear wall.

And that's the real Disney magic!

Nothing to see here.