As a new type of underwater acoustic sensor, fiber optic hydrophone is of great significance to China's utilization and marine strategy planning. To satisfy the ever-growing demand for low-cost, highly integrated, and high sensitive fiber optic hydrophones, there is an urgent need to advance fiber sensor technologies. A fiber Bragg grating (FBG)-based hydrophone exhibits advantages such as ease of large-scale array, cost-effectiveness, and high reliability, making it an important technical solution for the next generation of hydrophone arrays. This study comprehensively summarizes the FBG-based hydrophone based on the aspects of sensing systems, hydrophone probes, and key technologies. Additionally, signal demodulation at the dry end, which is a key technique in the development of FBG-based hydrophones, is addressed. This study has significant guiding significance for intensive research of key technologies, improvement of detection performance, and promotion of practical application of fiber grating hydrophone system.