No, and in fact there are submarine volcanoes, called guyots or seamounts.
Their molten rock spreads on the ocean floor and is eventually cooled by sea water, creating what is called pillow lava.
At depths below 6,600 feet high pressure prevents the explosive formation of steam that results when water meets molten rock at higher levels.
For example, during the volcanic eruption at Surtsey, an island off Iceland, there were explosions every three minutes equivalent to roughly 20 to 40 kilotons.
Something like an effort to drown a volcano was considered in 1973, when a volcanic eruption threatened the harbor of the island of Heimaey, off Iceland.
Sea water was piped in to try to freeze the advancing lava front in place.
For a time, a plan was also considered to use explosives to rupture the relatively cool crust on the part of the flow that had invaded the island’s harbor, permitting the sea water to quench the red-hot lava inside and thus check its advance.
However, experts calculated that if sea water came into contact with the hot lava under such circumstances, a steam explosion would rip open more of the lava, admitting more water, in what could become a chain reaction.
The experts feared that the reaction could propagate through the entire underwater body of lava, producing an explosion equal to a hydrogen bomb of several megatons.
It was create a disaster for the island and huge ocean waves that would threaten seaports around the rim of the North Atlantic.
The plan was called off, and the outpouring of lava eventually subsided, leaving the harbor usable.
