What hot springs in the ocean floor

Its when lava shoots right out of the ocean floors. Known as Hydrothermal vents 

In many areas of the ocean floor, wherever magma nears the seafloor, or where lava erupts directly at the seafloor surface, hot springs on the seafloor called hydrothermal vents commonly are found. Vent fields are generally associated with submarine (undersea) volcanoes where lava is erupting or preparing to erupt.