Crab Nest

Crab nests are structures found in oceans that spawn crabs.

Generation
Crab nests spawn in warm and lukewarm oceans (but not the deep versions) in the overworld. They are fairly common.

Blocks
Crab nests consist of sandstone, sea pickles, and 3 crab nest blocks.

Nests

Crab nests have 3 crab nest blocks, and thus are spawning places for crabs, spawning about 10 crabs every minute. This can be taken advantage of to create farms for crab shells and crab claws.

Lore
Crabs often lay their eggs together, usually around protected places such as large boulders. They will often kick up a lot of dirt and nutrients, allowing various plant life to grow there.