Swamp

The Swamp biome (known as the Swampland biome before 1.13) is a common lush biome. It has only one variant.

Description
Swamps are low-lying, damp biomes. The elevation often lowers enough to go under sea level, resulting in large patches of swamps being flooded. Water in swamps takes on a gray color on the surface, and turns pale yellow when submerged in it. Lily pads frequently generate on the water's surface. The non-flooded areas of the swamp feature relatively flat terrain, similarly to Plains biomes, though with significantly more trees. Trees that grow in swamps are covered in vines, not unlike the trees in Jungle biomes. Exposed grass and leaves in swamps vary in color, as swamps themselves have temperatures vary randomly, resulting in different shades of green for different patches of the swamp; typically, however, the color is a very dark, dull green. Despite the varying temperatures, it only ever rains in swamps.

Some parts of swamps have marsh-like terrain, where the grass has multiple single blocks of water generating within it. Sugar canes grow frequently in swamps, and huge mushrooms may grow as well. Blue orchids also exclusively grow in swamps. Occasionally, a witch hut may generate within swamps, with a witch inside. Swamps are additionally the only other biome aside from deserts where fossils can be found; they may rarely (1 out of every 64 chunks) generate underground. At nighttime, depending on the moon phase, slimes may spawn at Y-levels 60-80 alongside other hostile mobs, making swamps the only places outside of slime chunks where slimes can be found.

Survival in swamps can be somewhat easy if the player finds a large-enough clearing for a shelter. Wood supply is good without being overwhelming, water is abundant (though perhaps unpleasantly colored), and terrain is often flat. Witch huts can also be converted into witch farms, should the player want to easily harvest their drops. However, slimes spawning alongside hostile mobs can make nighttime survival more difficult if the player doesn't light up their surroundings.

Variants
Swamp biomes have only one variant, for a total of two different swamp biomes.

Swamp Hills
The Swamp Hills variant, known as Swampland M before 1.13, features hillier terrain rising up between the flat marshes. These hills are generally shorter than the hills in other biomes, though can still tower over the otherwise low-elevation swamp. Witch huts will not generate in swamp hills, nor will slimes spawn, but fossils may still generate underground.

Gallery
Note that images with blue water were taken before 1.13, which changed the color of water in swamps from blue to gray.