Vast expanses of the deep sea are cold and sparsely populated. Heat and chemicals spewing from hydrothermal vents, however, help support life in the surrounding area for fascinating creatures.

With the crushing weight of the ocean above, the extreme pressure–combined with high temperatures and chemicals toxic to other animals–makes this one of the most demanding environments on the planet.

Shrimp
Large numbers of deep-sea shrimp swarm the edges of hydrothermal vents. Some species have strange eyes on their backs that may be able to sense very dim light coming from the vents.

Tubeworms
Growing up to 3 meters (9 feet) tall, tubeworms have no mouth, eyes or stomach, but like humans, they have red blood containing hemoglobin. Tubeworms depend on billions of bacteria living inside them for survival: The microbes convert hydrogen sulfide, oxygen, and other chemicals spewing out of hydrothermal vents into worm food.

Snails and Mussels
At some hydrothermal vents, snails and mussels are the most common animals. They thrive in conditions that would be toxic to most other living things. This is possible because of bacteria living inside them, which use hydrogen sulfide and oxygen in the water to make food for the shellfish.

Many snail species have copper in their blood instead of iron (as humans do). This allows them to take in oxygen more easily from their low-oxygen surroundings. The copper causes the snail’s blood to be blue!

Vent crab
White in color, vent crabs grow to a width of five inches and live in large numbers around hydrothermal vents, feeding on deep-sea worms, clams, and mussels.

Zoarcid fish
The most common fish at vent sites, these pale, pinkish, eel-like creatures are also known as eelpouts.

Pompeii worm
The Pompeii worm breathes through the red, tentacle-like gills that cover its head and its grey, fleecy coating is made up of bacteria.

Clams
Dinner-plate-sized clams grow as long as 30 centimeters (12 inches) and reek of sulfur.