Which active volcano is currently underneath the water?

Loihi is the only active volcano among the choices listed that is currently underwater. It is located off the southeast coast of the Big Island of Hawaii and is considered to be the youngest volcano in the Hawaiian island chain. Loihi is still in the formative stages of its development and has not yet emerged above sea level, although it is recognized for its ongoing volcanic activity, including eruptions that can occur under the ocean.

Other volcanoes mentioned, such as Kilauea and Mauna Loa, are well-known for their eruptions and have significant landforms visible above sea level. Mauna Kea, while a dormant volcano, is the tallest mountain in Hawaii when measured from its base on the ocean floor to its summit. Understanding the characteristics and locations of these volcanoes provides insight into the geological processes that shape the Hawaiian Islands and the dynamic nature of the region's volcanism.