WHAT MAKES AN UNDERWATER THEME

[jcfiggy]

What, in your opinion, are some of the features that make a song just sound like an underwater theme?

To me, a perfect underwater theme would be something with long spaces between notes, drenched in reverb, with maybe some deep picked bass, synth or organ with 7th chords or even extended chords, and possibly a high-pitched instrument every once in a while to add something bright. Or not.