Distributed fiber-optic hydrophone (DFOH) is an underwater acoustic detection system based on distributed acoustic sensing (DAS) technology, which has the ability of long-distance and high-sensitivity continuous monitoring. A single optical fiber can multiplex thousands of hydrophone units, facilitating the construction of large-scale arrays, and enabling extensive underwater acoustic surveillance, thereby overcoming the scale limitations inherent in traditional hydrophone arrays. Firstly, the basic sensing principle of distributed fiber-optic hydrophones was analyzed, and key technological advances were explained from the wet end (hydrophone array), dry end (demodulation system), and array signal processing methods, with a focus on core indicators such as sound pressure sensitivity and equivalent phase noise. Then, the application overview of distributed fiber-optic hydrophone technology in recent years was introduced. Finally, summarize and prospect the existing problems and future development trends.