I. Introduction
With the continuous exploitation of marine resources, people’s awareness of protecting marine ecological environment is also increasing. The changes of distribution and quantity of marine organisms in a specific area can reflect the status of the ecological environment in that area. Therefore, Research on the habits and distribution of underwater organisms is beneficial to the sustainable development of fisheries and the protection of marine ecological environment. Underwater exploration by human hands is very human resource intensive and difficult to provide comprehensive and accurate observations. Currently, underwater robots have become an important device for underwater exploration, which can use cameras to sense the underwater environment and discover underwater targets quickly and accurately. The key to its mission is underwater target detection. However, the severe underwater light attenuation and the complex underwater environment bring challenges to the task of underwater target detection.