Worldgen Deeper Oceans

I've been attempting to add a new ocean biome with deeper depths than vanilla "deep ocean" biomes. How might I go about doing this? All the research I've done points to creating a noise settings json, a custom biome json, and an overworld dimension json (which I can't seem to find an example of that isn't over seven thousand lines long).
TL;DR: How might someone go about implementing a new "very deep ocean" biome?
(I realize this query might be asking a bit much, but it would be super helpful just to get some pointers to put me in the right direction)