There are lots of interesting eruptions through time. I'm interested in Krakatoa in Indonesia. This volcano erupted in 1883, causing widespread damage. It was well documented and it interesting scientifically. I visited the volcano in 1992.
Volcanoes occur under water as well as on land.
We study volcanoes where-ever they occur. Often we can learn about undersea volcanoes by looking at their on-land equivalents. Yes - the most famous example being a prisioner in the gaol at St. Pierre on Martinque in the Caribbean. These include active, dormant and extinct. When did the last volcano erupt in Costa Rica because I am studying it for a report.