Image enhancement is a widely used technique to increase the quality of an image. In this process the intensity levels are gradually increased in an image or parts of an image, results a quality image compared with the image captured at image acquisition process. These techniques are helpful to detect the edges or patterns present in the input images, used in different applications such as computer vision, medical imaging, underwater imaging and other multimedia applications to detect the objects or patterns in a given input image. Due to the degradation of color, light absorption and scattering, artificial light, suspended particles in underwater, the acquired images are having low contrast or very dim in color and causes only one color to dominate the entire image. Hence, the identification of the objects in the underwater image becomes tricky. After the image acquisition, preprocessing step is must to increase the quality of the degraded images for image processing and underwater or marine applications. This paper included numerous underwater image enhancement techniques developed in the recent years along with the limitations and challenges in it. © BEIESP.