In order to overcome the problems of low visibility and non-uniform illumination for underwater images,an underwater imaging model with non-uniform illumination was first derived based on the underwater imaging model with uniform illumination,and then a visibility enhancing algorithm was proposed from the developed model.In the algorithm,the mixing image with medium scattering light and light change was first estimated and eliminated quickly by using the low-frequency sub-band information of wavelet transform,and then the obtained image was segmented to bright speck region,and was scattering region and enhanced according to the segmented result respectively.The experimental results show that the proposed algorithm can significantly reduce the processing time and effectively improve the visibility of underwater degraded images while eliminating the effect of non-uniform illumination.Moreover,the processing results of consecutive frames of video sequence have good consistency.