Work songs sung by sailors between the 18th and 20th centuries are known as sea shanties. The shanty was a distinct type of work song, developed especially in American-style merchant vessels that had come to prominence in decades prior to the American Civil War. These songs were typically performed while adjusting the rigging, raising anchor, and other tasks where men would need to pull in rhythm. These songs usually have a very punctuated rhythm precisely for this reason, along with a call-and-answer format. Well before the 19th century, sea songs were common on rowing vessels. Such songs were also very rhythmic in order to keep the rowers together.