Considering the development of transparent ocean strategy, low-cost staring imaging equipment have unique advantages in underwater optical imaging. However, it is difficult to separate the backscattering and imaging target, as well as to capture a clear image at a long distance. More importantly, before acquiring the effective target image, the strong scattering noise saturates the image and prevents subsequent processing. Thus, we propose a novel imaging method that combines short coherent illumination and polarization imaging. The short coherent illumination simplifies the separation of the backscattering and imaging target while the polarization technology prevents image saturation in advance and ensures the effective acquisition of the target image. In addition, we built a large-scale underwater optical imaging platform and conducted imaging tests at a long-distance of 22 m. The experimental results showed that the signal-to-noise ratio increased from 0.50 dB to 13.57 dB, and the anti-image early saturation ability of the device increased 1.42 times. These results are superior to the traditional polarization imaging. The proposed composite imaging method can provide technical support for large-range underwater optical monitoring.