The focus of this paper is to describe research being conducted at NAVAIR in Patuxent River, MD to improve optical detection, ranging and imaging in the underwater environment through the use of optical modulation techniques. The modulation provides a way to discriminate against unwanted scattered light that would otherwise reduce detection sensitivity. Another benefit of modulating the transmitted light is that coherent detection of the modulation envelope results in the ability to accurately measure the range to the underwater object. Ways to use the hardware and methods developed for the detection, ranging, and imaging scenario to satisfy other mission requirements are also being investigated. The requirements for the modulation scheme, modulation frequency, and laser characteristics (pulsed, continuous, optical power level) depend on the targeted application. The implementation of this optical modulation technique in a variety of underwater sensors has become possible due to recent advances in laser and receiver technology. A review of the work being done in this area of research will be presented, and results from laboratory experiments will be discussed.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.