Yes, most volcanoes are located under water at the mid-ocean ridges. They can be one of the reasons that tsunamis happen.
They are volcanoes underwater.Seamounts
seamounts
All volcanoes have some dangers, of course. Some underwater volcanoes can lead to tsunamis or other forms of water disasters. Land volcanoes spit ouot hot ash and lava and molten rock, and smoke as...
they erupt just like they do above water