Abstract: Recent significant advances in the design and technology of underwater acoustic transducers are reviewed. These include the development of functional materials for transducers, and new designs based on new materials such as rare earth giant magnetostrictive materials, relaxor ferroelectrics and piezoelectric polymer films. Novel types of transducers with innovative structures or different energy transfer mechanisms, and the most recent technology for broadband transducers are described. In the category of receiver type transducers discussion is focused on the fiber optic hydrophone and vector hydrophone.