An acoustic underwater navigation system is disclosed. For instance, an underwater receiver determines its position using signals broadcast from an array of acoustic transmitters located near the surface. The position of the array is measured using global positioning system (GPS) technology and the transmitters collectively produce an acoustic signal in which the position and attitude of the array and the GPS time of transmission are encoded. An underwater receiver which is synchronized with the GPS time uses the transmitted position and attitude of the array and the transmission time information to calculate its position.