Abstract: With the in-depth implementation of the marine power strategy, the deficiencies of traditional marine structural and equipment materials, dominated by high-strength steel, in terms of performance and durability have become increasingly prominent. There is an urgent need to develop novel alternative materials to address the challenges faced by metallic materials in the marine environment. High-performance thermoplastic composites, with their characteristics of being lightweight, having high strength and toughness, excellent high-temperature and fatigue resistance, strong design flexibility, easy formability, and reparability, show great potential for application in underwater marine structures. This paper reviews the research progress on the application of high-performance thermoplastic composites in underwater marine structures. It focuses on analyzing their moisture absorption behavior and mechanical property stability in seawater, and details the performance and technical advantages of the material in key applications such as marine propellers, underwater thrusters, marine risers, and deep-sea pressure vessels. The current challenges in this field are also pointed out, with the aim of providing a reference for further research and application of high-performance thermoplastic composites in underwater marine structures.