U-boat.
A submarine is an undersea boat, or submersible.
Submersible.
In World WarII, the germans named it a uboat
underwater craft, submersible, U-boat
Another name for a submarine is a submersible. Submersibles are watercraft that can operate underwater, typically used for military purposes, scientific research, or underwater exploration. These vessels are capable of navigating beneath the surface of the water for extended periods of time, often equipped with advanced technology for communication, navigation, and life support systems.
The Nautilus was Fulton's submarine.
Below
plunger is a fitting name for submarine because , it is under the water
this word is an adjective meaning "under the sea". submarine is the word shortened from the term "submarine boat".
Submarine
The H. L. Hunley was the name of the Confederate submarine that was the first combat submarine to sink an enemy ship.
The Confederate submarine 'H L Hunley' was the first submarine to sink an enemy ship