Most intelligent underwater vehicles and remote control marine vehicles are usually equipped with optical cameras for underwater photography. However, due to water properties and its impurity, the quality of the images taken by these imaging equipment is not desirable, enough. Because, water reduces the light and by increasing the deep of water, the further light will diminish, which will result in the absorption of colors by water. Hence, image processing operations are crucial for underwater images .In this paper, a new method has been proposed to improve the contrast and quality of underwater images. In the proposed method, the two methods of contrast stretching and histogram equalization have been employed. In the histogram equalization phase, new methods have been introduced for thresholding and histogram clipping. The proposed method has been applied on a benchmark images dataset and the results have been compared with the results of common methods. The analysis of the proposed method results, compared to the Sathya et al., which is the best method compares to other rival methods, shows 40.16% increase in the contrast of the images, in the best case