River

The River biome is a common technical biome. It serves as a border between various other biomes, and usually leads to an ocean biome, though can occasionally form a circle. It has only one variant.

Description
Rivers are thin, lengthy biomes that frequently generate across the world. They typically serve as a division between two different biomes, but can occasionally split a single biome in two. They are filled with water up to sea level, though rivers may run dry in certain areas due to higher than usual elevation. Exposed grass in river biomes takes on a bluish-green hue. Riverbeds consist of dirt, sand, gravel, and clay, and are the only places where clay generates aside from occasional large lakes. Seagrass generates atop the riverbed, and sugar cane occasionally generates on the riverbank. Passive mobs cannot spawn within river biomes themselves, but frequently wander into them from the surrounding biomes if they can spawn there. Hostile mobs can spawn within rivers, however, and drowned can spawn underwater, as can salmon.

When generated between two high-elevation biomes, such as mountains and hills, river biomes may pose a fall damage hazard, but are otherwise mostly harmless. Rarely, a shipwreck may generate in a river. Due to the river's relatively small size, however, generated shipwrecks are likely to have some generation faults, and may need to be extensively dug out.

Variants
River biomes only have one variant, for a total of two different river biomes.

Frozen River
Frozen Rivers only generate within snowy tundra biomes. As the name implies, the top layer of water is entirely frozen, though below the ice is the usual sand, gravel, and clay. Shipwrecks do not generate in frozen rivers. While sugar cane can generate alongside a frozen riverbank, it quickly uproots itself after generation due to the water being frozen. Along with drowned, strays can spawn in frozen rivers.

Note that regular rivers can still cut through snowy tundra; in this case, they will only be partially frozen, leaving the middle of the river liquid.