The purpose of the proposed project is to provide an algorithmic design of a system for the detection, localization and classification (altitude/depth and yield) of a remote detonation at sea using hydroacoustic data. This information can be obtained from the signal power spectrum levels, signal arrival times and reverberation time histories observed by the monitoring hydrophones and estimates of the acoustic propagation conditions between the detonation and the hydrophones. Such information would provide clues as to whether the detonation was nuclear or non-nuclear, purpose and sophistication of the detonating device and also the identity of the testing nation. This Algorithmic design will involve the development of some new algorithms from existing theory, the adaptation of existing algorithms and the integration of these algorithmic components into a single, coherent unit. It will also involve the estimation of the potential accuracy of an implemented system. This would provide a basis for determining the utility of the software, hardware and staffing implementation of the system in subsequent program phases.