This is a
"black smoker" - a deep-sea
hydrothermal vent. (Credit: NOAA)
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots.
These vents may have ecosystems of a kind that we don't see anywhere else. Instead of sunlight, the energy source is chemical energy from minerals - bacteria that can turn the chemical energy into food are the bass of the food chain. They have the same role in the ecosystem as plants do in most surface systems.