Underwater image processing is a difficult topic in the field since the environment of underwater is complicated. The major difficulty is that a captured image is fuzzy, under-exposed and has the color cast since the light is absorbed and scattered. To overcome those difficulties, we propose a new underwater image enhancement method, which is composed of an underwater image dehazing algorithm and a color correction algorithm. Based on the dark channel prior and the characteristic of light propagation under water, we propose a new dehazing algorithm to restore the visibility of degraded underwater images, through building up the relationship of the transmission rates among three color channels. To further improve the quality, we propose a simple yet effective color correction method to solve the color cast of the obtained haze-free underwater images. Experimental results show that our method can improve upon several existing methods in both subjective and objective tests.