Kelp

Kelp is a form of seaweed and also a renewable resource that can be used for food, farming, and crafting. It was introduced in version 1.1.

Appearance
This growing organism has a green slender appearance with a long curvy thallus and leaf-like blades. They are permanently anchored to the sea floor, can grow up to the surface of the water, and sway to otherwise unnoticeable currents.

Loose pieces of kelp are mottled dark green that have the appearance of a mesh spreading from a narrow, flat base.

Where Found
Kelp typically grows in temperate to equatorial coastal waters that do not see seasonal freezing in the winter. They can be found in water up to at least fifteen (15) blocks deep.

While kelp will try to spawn and grow in arctic waters, it will despawn in any water block that changes to ice. Occasionally a piece of dropped kelp will be found on top of recently formed ice. Most of the time, however, it's trapped under the ice and held there until it despawns or the ice melts. In places where ice melts soon after it forms, loose kelp pieces may float to the surface where they can be picked up by swimming or boating.

Farming
Kelp can be farmed by planting it in almost any type of block under at least one block of water. It is possible to plant kelp in only half a block of water. Water depth is important because kelp will not grow above the highest (at least partially filled) block of water above it. Care must be taken to avoid drowning while harvesting kelp in deep water.

Harvesting kelp by hand produces one unit per block, but using a machete or spade will usually produce three. Kelp above a harvested segment will despawn and may not produce any kelp, so for maximum yield kelp should be harvested from the top down. Leaving the bottom-most block of kelp in place when harvesting avoids the need for replanting, thus farming kelp is more effective when the water is more than one block deep.

Crafting
Kelp is the only ingredient in crafting compost and can be done at a craft bench.

Other Uses
Kelp is edible, restoring health and hunger bars when eaten.

When eaten, Kelp will replenish about half the total of a blockhead's depleted air bar.

Fish may spawn in the vicinity of growing kelp, and after having grown long enough in a large enough area, because of the many fishes, sharks may start to spawn.