The name U-boat was applied to German submarines.
They were called U-boats - Unterseeboot which means undersea boat.
the German "U-Boat".
The submarines were either called "submarines" or "U-boats." The German submarine was called the "U-boat"
A German submarine used in WW I was called a U-boat.
U-Boat
Underseaboat.
The Dumbo Ship
A U-boat was a submarine used by Germany in World War 1 and World War 2.
U-boats
German submarine warfare
The term U-boat comes from the German word for submarine, and it was usually used only in reference to German submarines, and not those of Japan or the US.
Underseaboat.