Abstract <p>In response to the current problem of unsatisfactory enhancement effect and low image processing efficiency of underwater images using dark channels, an improved algorithm based on dark channel priors is proposed to process underwater images. The method based on median filtering is used to obtain the atmospheric transmittance <i>t</i>, which improves the efficiency of atmospheric transmittance <i>t</i> acquisition under the premise of ensuring the defogging effect. The quadtree image segmentation method is used to obtain the global atmospheric light <i>A</i>, which improves the image processing effect. Aiming at the problem of insufficient saturation of the image and low contrast of local details, the image is transferred to HSV space and enhanced by adaptive saturation adjustment and Gamma correction respectively. Four images are selected for experiments and analysis. The results show that compared with the original algorithm, the improved algorithm increases efficiency by about 34% while ensuring the defogging effect. Moreover, the improved algorithm restores more detailed information in the image and removes the fog from the image effectively.</p>