Having been under the sea for many years, ancient cultural relics have adapted to the surrounding chemical, physical and ecological environments, and have achieved a balanced state of preservation. In this paper, we summarize the impact of underwater burial environments on cultural relics, and elaborate on the protection methods applied at various types of underwater cultural heritage sites (e.g. ancient shipwrecks, settlement sites) by developed countries, and discuss their related research results. We hope that this paper will provide references for relevant research work implemented in China.