Abyss biomes ideas

That are some ideas that i would like for new abyss biomes (you can take some inspiration from that):
a) Id like a very deep area with few form of life and a giant scary leviatan (deepth: 2000-3000 meter) with a wreck of alterra submarine
b) another abyss type biome with a leviatan hidden in the sand (or other thing) that will jumpscare and exit if the player get close (deepth:1000-2000 meter)
c) another type abyss area but in a more closed space (like caves) that will contain like a big muray with sharp teeth (deepth:1000-2000 meter)