Underwater

The  is an aquatic biome located below the Ocean which generated upon world creation, it has an entrance located from the center area with the funnel shape hole that is similar to the Underground Desert.

The is home of many deadly enemies, since is underwater, is more difficult to avoid from their attacks.

Some features from the :
 * Shipwreckss (an Underwater-themed Underground Cabin) randomly generated at world creation.
 * Pearl can be mined from any pickaxes with 55% or higher pickaxe power.
 * Upon entering Hardmode, has a low chance of Evil Biome to spread and starts spawning Aquatite Ore.
 * Upon entering Supermode, Leviathan's Eggs begin spawning.

Enemies

 * Pink Jellyfish
 * Shark
 * Squid
 * Sea Snail
 * Green Eel
 * Diver Skeleton
 * Giant Clam
 * Sea Urchin
 * Queen Jellyfish (boss)

In Hardmode:
 * Angler Fish
 * Hermit Crab
 * Giant Moray
 * Octopus
 * Sea Mine
 * Sea Mimic (rare)

Post-Plantera:
 * Devil Angler
 * Box Jellyfish

Post-Golem
 * Siren
 * Merfolk
 * Killer Whale
 * Electric Eel
 * Giant Isopod
 * Kraken (boss)

In Supermode:
 * Great White
 * Giant Squid
 * Sea Tortoise
 * Dragon Fishron (rare)
 * Leviathan (boss)

In Ultramode:
 * Brittle Star
 * Abyssor, The Sea Guardian

Unique Drops
Enemy Drops

Terrain Drops
 * Coral
 * Seashell
 * Starfish
 * Bubble
 * Coral Block
 * Kelp
 * Sea Bulb
 * Marine Rock
 * Dark Marine Rock
 * Pearl
 * Aquatite Ore

Trivia

 * The background music use is a remix version of the old-gen console Terraria Ocean music.