Propulsion. Propulsion provides the forward motion. The actual motion itself is called by the nautical term "way" as in "under way". It is the same term as applied to a surface ship and comes from the time well before steam power.
A submarine.
A vessel that travels underwater is termed a submarine.
A submarine is a ship that can travel underwater.
An underwater volcano is called a submarine volcano.
The little underwater boat on Club Penguin could be either a midget submarine or an untethered submersible. Its smallness and agility make a good case for calling it a submersible. In the Aqua Grabber instructions they call it a 'sub', which is usually short for submarine but could actually refer to either one.
I dont know what you call 5 blondes underwater.
Fulton named his submarine Nautilus
A sea version of a volcano is called an underwater or submarine volcano. These volcanoes erupt beneath the surface of the ocean, releasing magma and gases into the water. They can create new islands or extend the size of existing ones.
Submariners.
He is a submariner.
seamount
what do we call the energy motion