A caldera is usually the remnant of a volcanic eruption powerful enough to collapse the structure surrounding the magma chamber. Many of our examples, like Yellowstone, Crater Lake, Toba and even Ngorongoro, are inland, hundreds of miles from any seawater. The only exception I can think of is Santorini. When it erupted some five thousand years ago, it must have measured 6 on the VEI scale, a colossal eruption, turning one island into several.
So with those examples in mind come this particular question. Inland calderas are one thing, but what about inshore calderas? Is it possible for a Ring of Fire eruption, like in the Andes or in Japan, to release a strong enough eruption to collapse many square miles of land to the bottom of the sea, thus creating a flooded crater?