(I'll respond to stuff in part 2 to that comment)
A distorted opening theme (Which I've been informed is the latter part of "We Are The Crystal Gems") would definitely be a bit unnerving, given that you hear it so often and it's so closely linked to the characters!
I'll be completely honest, "Battle at the Underwater Temple" was probably the only song on here I had never heard! On my first listen through I skipped around the soundtrack, and after subsequent runs straight through, I'd always skip this section to avoid the likes of "Big Fat Zucchini", tracks I just couldn't like. But I would also skip "Battle at the Underwater Temple" because I assumed I had listened to it and it was unmemorable :(. Upon a few cursory listens, here are my thoughts:
I think you'd agree that "Battle at the Underwater Temple" is one of the most unique tracks on the whole soundtrack. This is primarily due to the unique place of the electric guitar, that using a central lead role rather than filling a rhythmic one, which is common on the soundtrack. This gives the song such a unique characteristic to it, it's hard to imagine why that is without seeing the episode! Not that I won't try...
In the picture for the "Steven and the Stevens" songs, we see Steven holding an electric guitar, so I'm going to assume that it represents him. Even given that, this track is all over the place. It begins with the same mythic vibe given off from songs like "Mirror Match" because of that choir, but the guitar picks up the pace and brings out the drum beat more. In this way, the guitar (Steven )served to accentuate the frantic nature of this battle. After this, a slow and frankly cheesy guitar and strings combo lead us to the final mythic-sounding half minute. The cheesy vibe was used in most of the "Steven and the Stevens" songs, so that's why assume I'm right in calling it here. I'll have to watch and see why they made it how they did, but the central role of the guitar is definitely indicative of some uncharacteristic battling going on in this Temple. It also makes me want to break out my old guitar and jam just as much as "What Can I Do" :)
I'm going to edit this comment at a later time, and then respond to part two. I'm already running a bit close to the clock...
See all you Steven Universe fans tonight!