We have at least two examples of this happening in historic times
Krakatoa
Krakatoa is the most powerful volcanic event in recorded history, the explosion being heard almost 3,000 miles away. The people living in the area knew that the land they were living on was volcanic, but it seemed to have a small caldera. What they didn’t realize was that the caldera was actually hidden underwater and what appeared above water was just the eroded edges of the caldera.
70% of that land collapsed into the underwater caldera when it finally erupted after several months of smaller earthquakes in August 1883.
The largest explosions are estimated to have been several times larger than the largest nuclear device ever used, and caused tsunamis.
The group of islands has been changing ever since with new islands being formed, but ones made up largely of ash disappearing after a short period of time. A new island appeared above the main cone about 40 years ago and is still growing slowly.
Surtsey
Surtsey is one of the best documented underwater eruptions of all time, although it’s not nearly as impressive as Krakatoa.
Surtsey in 1963. 16 days previously, there was nothing but sea there. It’s likely that the eruption started before that and went unnoticed until it reached the surface.
The eruption continued until 1967. Since then, the island has been slowly eroding away, even though its peak is still 500 feet above sea level.
Surtsey in 1999.