The fourth Minecraft dimension is really exciting to me! I won't be discussing all the leaks I've heard but I will be sharing an image that is near definitely THE dimension. Read below at your risk! (This has been in my drafts for days, you probably saw it already lol)
"going to feel like an underwater biome, but with the water missing" is what the original concept of the Deep Dark was going to be, and surprise surprise... what does this image invoke if not that exactly? This concept art can be found on the launcher itself as the background, so we know it's still decently accurate.
i think this floating goober is based off the Anomalocarididae, it has the front appendages and tail thingies. The other floaties seem to be soft bodied jellyfish, like this guy below!
this jellyfish creature shows us that even if the previous creatures don't appear, there will still be floating sea life. It could be that the other creatures are herbivores, filter feeders, or just prefer to dangle their tendrils and wait for prey, while these jellyfish are more active predators. We'll have to wait and see... speaking of sight, they do appear to have what looks like an eye, wether this is a true eye or not is yet to be seen. They also have that paler yellowed skin, possibly showing that it will open up like the next group of creatures.
These three are interesting, they obviously share a resemblance to the Great Hunger (Mob C) from the first official mob vote. The smallest variants appear to be about the size of a block and bald, the thicker taller variants have a bit of a Mohawk-fin-frill thing, and the variant with the long legs has its little dangly bits.
Uhhhj, this has been in the drafts for too long. I intended to make a master 4th dimension post, buuuut new info comes daily at this point so uhhh. Hit post.