Sunken Sea

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A hub of diverse ocean life, and all that remains of Ilmeris that is unscorched.

Marine Biology Log

The Sunken Sea biome, as viewed on the map in a large world.

The Sunken Sea is an aquatic biome added by the Calamity Mod which spawns upon world creation. It is located directly underneath the Underground Desert. Comprising it is a series of caves almost entirely filled with water, illuminated by glowing blue Prism Shards.

It is filled with numerous sea creatures, most of which are peaceful until provoked, including the Giant Clam mini boss. The biome becomes more populated once Hardmode begins, and several existing enemies receive new abilities and item drops.

It is composed primarily of Navystone and Eutrophic Sand, as well as Prism Shards scattered throughout. Giant floating Geodes are located throughout the biome, which are composed of a Navystone shell and Prism Shards attached to Sea Prisms inside. There will always be a Geode at the center of the entire biome, which is also the largest Geode. A large variety of different corals and other ambient objects also generate in this biome. The Table Corals can be stood on, the Fan Corals produce light, and the Brain Corals can produce bubbles that the player can touch to gain the Gills buff, with small ones granting it for half a second, and larger ones granting it for 1.5 seconds.

The unique Sunken Sea Bio-center Lab is also located at the bottom of the Sunken Sea, containing the schematic used to craft the first tier of Draedon's arsenal and decrypt the second schematic.


Unique Drops
From Ghost Bells after defeating Desert Scourge:
From Prism-Backs after defeating Desert Scourge
and Blinded Anglers:
From Blinded Anglers:
From Giant Clams after defeating Desert Scourge:
From Clams and Giant Clams in Hardmode:


Map Background Abyss Layer 1.png
Sunken Sea Bestiary and Map Background.
  • Player-created Sunken Sea biomes are possible by placing more than 150 Eutrophic Sand, Navystone, and/or Sea Prisms in an area.
  • The player is also considered to be within the Sunken Sea when standing in front of natural Eutrophic Sand Walls or Navystone Walls.
  • It is possible to find Lime Kelp in the Sunken Sea.
  • Only Sunken Sea enemies can spawn while the player is considered to be in the biome, and only in areas that have water. If there is no water or the only areas that have water have player-placed walls, no enemies can spawn.


  • Equipping any accessory which allows for extended or infinite underwater breathing (such as the Ocean Crest or Diving Helmet/Gear) will make exploring this biome much easier.
  • The Sunken Sea is a good place to go to obtain Life Crystals early in a playthrough; there are no traps, none of the enemies are naturally hostile, and the area is intermittently lit up by Prism Shards to make finding them easier. There are many places where the Sunken Sea can naturally be entered, and there are usually Minecart Tracks that open paths to explore even more of the Sunken Sea.
    • Note that other aquatic enemies (such as Jellyfish and Piranhas) can spawn in the Sunken Sea before the player is considered to be in the biome, so exercise caution when entering.
  • As the biome contains essentially no hostile enemies spawns and its blocks have no corrupt, crimson, hallow, or astral variants, it is one of the safest places the player can put their home base, provided they can drain the water. Remember that Eutrophic Sand Walls will continuously spawn water, so removing them is advised to avoid the player's base being flooded.
    • Creating an artificial Sunken Sea is an alternative strategy for making a home base, however the surrounding areas will still be vulnerable to spreading biomes.


  • In the mod's lore, the Sunken Sea is the last remaining part of Ilmeris when it was incinerated by Supreme Witch, Calamitas.
  • The theme heard while in the Sunken Sea is sanctuary, which was composed by the artist DM DOKURO.
    • The song's motif is the same as that of the theme of the Sulphurous Sea.
    • If the Calamity Music add-on mod is disabled, the Ocean's nighttime theme will play instead.
  • Many of the enemies or items having the word "Eutrophic" in their names suggests that the Sunken Sea has undergone some degree of eutrophication, which results in an oxygen-depleted environment.
  • Oxygen depleted environments can lead to lethargic sea life in the real world, which may explain why the majority of this biome's enemies are passive until provoked.
  • Brain Corals producing oxygen bubbles may be a reference to the game Subnautica.
  • During the generation of the Sunken Sea in world creation, the message reads "Making the world more wet." This phrase was originally used to tease the implementation of the biome in the mod's changelogs.


These history sections are still a work-in-progress, and may not yet contain changes relevant to the current version of the Calamity Mod.
  • Added more ambient coral variants.
    • Added new visual effects for water.
    • Added new underground background.
    • Improved biome's generation in general.
    • Now always generates at the very bottom of the Underground Desert.
    • Smoothened by worldgen again.
    • Now generates after vanilla to prevent traps from appearing in.
    • Water is now clearer.
  • Reused the Abyss layer 1 map backgrounds to it.
  • Now generates before the Jungle Temple.
    • Fixed corals blocking out light.
    • Fixed it counting as the Brimstone Crag in some cases.