Kelp

Kelp is an underwater plant that generates in most ocean biomes, except frozen, deep frozen, and warm oceans. It can be harvested instantly with any tool and drops a Kelp item when broken. Kelp can be placed underwater on various blocks and naturally converts downward-flowing water into source blocks, which helps when building bubble column elevators. It can be smelted into dried kelp, which can be eaten or crafted into dried kelp blocks for fuel. Kelp can also be composted, with a chance to raise the compost level.

Kelp grows naturally, increasing in age with each growth stage. It stops growing once its age reaches 25. Bone meal can be used to accelerate its growth. Harvesting the top block resets the age of the Kelp below, allowing for taller-than-normal growth. Kelp farming is similar to sugar cane farming but is easier to automate due to items floating to the surface when harvested.