Seagrass is a non-solid plant block that sways underwater in rivers, frozen rivers, non-frozen oceans, swamps, and mangrove swamps. Shears are the only harvesting tool, since any other tool, item, or a bare fist destroys Seagrass and drops nothing. Regular plants cut with shears drop themselves as items, while tall plants drop 2 Seagrass items. Tall Seagrass, the two-block-high variety, exists only as a placed block — Creative mode and commands offer no tall item form. Bone meal used on an underwater block sprouts fresh plants on that block and its neighbors when 2 water blocks sit above and the lower one stays still. Bone meal farming makes Seagrass a renewable resource players can regrow endlessly.

Turtle care is the main use: holding Seagrass leads turtles, feeding two adults starts breeding, and feeding a baby turtle speeds up growth. Each Seagrass item gives a composter a 30% chance to raise the compost level by 1. Bone meal applied to a regular plant transforms the plant into tall Seagrass when free space sits above. Lava flowing toward Seagrass stops completely, so builders can float lava on top of a water column.