A period of time on duty. The crew is divided into two watches, larboard (port or left) and starboard (right). Each group spends four hours on deck, while the other is on break. The larboard watch is commanded by the first mate, and the second mate leads the starboard watch. One shift is divided into two, two hour shifts called dog watches. This creates seven watches in a day, the odd number preventing either watch from having the same shifts day in and day out.