Aside from working images/sprites, what the content in this post really needs is some variety. Most of the items and enemies here are focused around a single debuff.
Try adding stuff that isn't related to the Inky debuff, maybe some sort of beautiful glowing jellyfish miniboss that shoots electricity at you, or an item that allows you to transform into a bobbit worm. The point is, don't make everything from the biome inflict Inky.
As well as this, you should add some content that make the Deep Ocean a biome worth exploring. Think about what other biomes have that make them fun/important to explore. I'm not saying to add another "soul of __ight" item, just make it have stuff that's
worth obtaining that fits the biome's theme. And as
@Bame Jouvier said, try to balance it as best as you can, perhaps make some parts of the biome restricted until a certain boss or event is defeated. A biome isn't a good biome if all it has is a few non-special enemies and a lousy item or two.