Underwater image and video normally suffer from some problems such as blue-green illumination, low color and contrast, induced under- and over-enhanced areas, and less detail. These problems restrict the important information to be extracted from the image or video for further processing. Nevertheless, these problems limit further applications of the image and video such as in object detection and tracking, as the information is covered by blue-green illumination of the water. This book describes in details about the enhancement techniques of underwater image and video to reduce the above-mentioned problems. The proposed techniques are based on histogram modification and could be applied and implemented for underwater image and video. Histogram modification could be regarded as the simplest method of enhancement and requires less computational complexity. Through the proposed techniques, the aforementioned problems are significantly reduced and the image and video are successfully improved especially in terms of color and contrast. In addition, the blue green illumination and under- and over-enhanced areas are adequately reduced.