Abstract: In underwater location, accuracy of images are degenerated by light absorption and scattering. Underwater image enhancement is use for colour control in the underwater image. There are discussing two method of underwater image. Firstly, the contrast stretching of RGB algorithm is applied to equalize the colour contrast and brightness in images. Secondly, the saturation, hue and intensity of underwater image to increase of real colour and solve to the problem of lighting moves in underwater. Generally Mat lab software are use for underwater image enhancement. A novel method to enhance underwater optical images by dehazing. Scattering and attenuation are two major problems of distortion for underwater imaging. Scattering is caused by large depended particles, like fog or turbid water which contains sufficient particles, plankton etc. attenuation according to the varying degrees of attenuation encountered by light traveling in the water with different wavelengths to the according different underwater colour image. The underwater image enhancements techniques are use for reduced noised level, haze, fog, better possibility of the dark regions, increase global contrast and edges preserving smooth. The quality and visibility of underwater images is damage than atmosphere image and images usually appear foggy and hazy.

Keywords: Underwater optical Image; Underwater visibility enhancement; Guided filter.