Subsurface adds 11 new cave biomes to the overworld and nether. Subsurface cave biomes can generate inside of other vanilla cave biomes, creating hybrid cave biomes, and are compatible with almost all other datapacks/mods.

Cave Biomes

Icicle Caves

Icicle caves can spawn under snowy non-mountain biomes. They contain Icicle on the celling and the floor, and ice patches, which have blue ice if they replace deepslate. Aquifers in this cave biome are frozen over. Be careful when placing torches, as they could melt the ice and wash the torches away.

Sand Caves

Sand caves can spawn under the desert biome. They contain sand and sandstone patches. Some of the sand spawns floating, so be careful not to cause a cave-in.

Swamp Caves

Swamp caves can spawn under the swamp and mangrove swamp biomes. They contain mushrooms, dead bushes, vines, and patches of clay, mud, water and various dripleafs. Aquifers in this cave biome have lily pads and seagrass patches.

Underground Forest

Underground forests can spawn under biomes that generate oak trees. The ground here is covered in grass, and they contain mushrooms, vines, patches of coarse dirt, and oak trees. glow lichen spawns on the leaves

Coral Caves

Coral caves can spawn under the warm ocean biome. They only exist in aquifers and water caves. They contain coral, kelp and seagrass.

Foliage Caves

Foliage caves can spawn under jungle biomes. The ground here is covered in grass and ferns. Jungle bushes, jungle trees, mega jungle trees, and bamboo spawn here, and the caves contain mushrooms, vines, and glow lichen on the celling of large caves. Aquifers in this cave biome are made of mud and have seagrass patches. Caves that spawn close to the surface can have skylights.

Fungal Caves

Fungal caves can spawn under the mushroom island biome. The ground here is covered in mycelium, and large and small mushrooms. this biome also contains hanging mushroom roots, wall mushrooms, and glow lichen patches.

Mesa Caves

Mesa caves can spawn under mesa biomes. They contain red sand and red sandstone patches. colored terracotta spawns here, as well as terracotta plateaus.

Underground Taiga

Underground taigas can spawn under biomes that generate spruce trees. The ground here is covered in grass and ferns, and they contain mushrooms, vines, patches of coarse dirt, spruce trees, mega spruce trees, sweet berries, pumpkins, and mossy cobblestone rocks. glow lichen spawns on the leaves.

Soul Canyons

Soul canyons spawn in the nether in the nether wastes and soul sand valley. The ground here is covered in soul sand and soul soil. They contain nether wart, soul fire, fossils, giant nether warts, and weeping vines and nether wart blocks on the celling.

Quartz Canyons

Soul canyons spawn in the nether in the crimson and warped forests. They contain giant quartz crystals, and quartz ore can be found in the surrounding netherrack.

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Also check out: https://modrinth.com/datapack/better-lush-caves