Maritime patrol is the task of monitoring areas of water. Generally conducted by military and law enforcement agencies, maritime patrol is usually aimed at identifying human activities. Maritime patrol refers to active patrol of an area, as opposed to passive monitoring systems such as sound-detection fixtures or land-based spotters. A patrol consists of a ship, submarine, aircraft or satellite examining the patrolled area and seeking out activities to be identified and reported. Maritime patrol is critical in wartime situations for navies to locate enemy forces to engage or defend against. Peacetime patrols are important for interdiction of criminal activities and for ensuring legal use of waters.