Scientists long thought that life couldn't exist at hydrothermal vents deep in the ocean. But in 1977, they found giant tubeworms living along the Galapagos Rift, 8,000 feet below the ocean's surface. These tubeworms are surrounded by total darkness in their habitat and they live in water filled with toxic gas and acid.
These creatures have no stomach, gut, or eyes. Instead, they are "bags of bacteria" with heart-like structures and reproductive organs. The bacteria inside the worms use the toxic hydrogen sulfide in the water, which would kill most other animals, as an energy source to produce carbohydrates.
Source: National Geographic