What was the nickname of German submarines during World War 1?

U-boat is the anglicized version of the German Word U-Boot , itself an abbreviation of Unterseeboot (undersea boat), and refers to military submarines operated by Germany in World War I and II. The primary targets of the U-boat campaigns in both world wars were the merchant convoys bringing supplies from Canada and the United States to Europe. Austrian submarines of World War I were also known as "U-boats". The distinction between U-boat and submarine is common in English-language usage (where U-boat refers exclusively to the German vessels of the World Wars) but is unknown in German, in which the term U-Boot refers to any submarine.