Acoustic radiation is the obvious choice for underwater surveillance because of its long-range penetration. This course commences with underwater acoustic propagation and attenuation, acoustic beam formation and electronic steering, the sonar equations, and describes the operation of a representative selection of sonar arrays (both active and passive). The second part of the course deals with the scientific fundamentals of navigation systems and their use in the guidance of machines and humans. It is developed from the point of view of the scientific principles involved and their application in the military, civilian and research environments. Topics include accurate time-keeping, underwater and satellite-based navigation, celestial, GPS and inertial navigation systems and their integration to produce state-of-the-art navigation capability.