In reply to:

like it might sound underwater to tiny ears if someone tapped hard on the glass wall.


Fish don't have ears, then have something that is called "lateral lines". Look at a typical aquarium fish, you'll see a line that starts at their head and goes all the way to their tail. Because of these lateral lines, fish hear very well and tapping on aquarium glass very likely sounds like an explosion to them!

By the way, the Darla Tapping scene is by far the most thunderous test I've seen of my PC-Ultras so far!

- Bill