Sound can travel much greater distances underwater than radio waves. As a result, applications which use radio waves in the air, such as radar, must use sound in the ocean. That fact, along with advances in small, high performance computing systems, is making many new applications of underwater acoustic systems possible. This research program seeks to explore opportunities using underwater sound - specifically the technique of Doppler sonar - in oceanographic studies. Applying the same principles used by police radar, Doppler sonar systems are routinely used for measuring water currents. We propose to apply existing Doppler systems to new applications and to develop new Doppler systems for use where existing technology is inadequate. Three new areas of velocity measurement are considered in this research program; near bottom speeds, fish speed measurements, and water speeds where deep-water corals occur. New instruments are being developed to measure water velocity in the 10 cm above the ocean floor. Such near bottom measurements are not possible with existing instrumentation, but they are needed to understand the erosion of beaches in storms and to predict the movement of silt that must be dredged from harbours. Existing Doppler systems normally exclude signals from fish, but by analysing those signals, it is possible to extract fish swimming velocity; such a capability would provide fisheries regulators with valuable data on the movement of fish populations. A third area of application is the measurement of ocean currents where deep-water corals occur at depths between 300 m and 2500 m on the east coast of Canada. An improved understanding of the environment needed for deep-water coral growth is essential to developing management strategies that can limit damage caused by offshore fishing. The results of the proposed research will impact future policy and regulations important to Canada; measurement of sand movement is central to harbour maintenance programs, sustainable fisheries require informed management, and protection of deep water coral habitat is needed to maintain healthy ocean ecosystems.