Large volcanoes that rise from the sea floor are called seamounts.

Here's some additional information:

* Seamounts are underwater mountains that don't reach the surface of the ocean. They are often formed by volcanic activity and can be found in all the world's oceans.

* Guyots are a specific type of seamount that have a flat top. This flat top is usually the result of erosion by waves when the volcano was once above sea level.

* Volcanic islands are volcanoes that have risen above the sea level and formed islands.

I hope this helps!