Fiber optic sensors are expected to become an auxiliary measurement method in the field of ocean observation due to their small size, easy networking, and intrinsic resistance to electromagnetic interference. Recently, the research of optical fiber sensing technology in the field of physical ocean observation has received broad attention from scientific researchers. According to the different classifications of measurement objects and principles, this article focuses on the seawater temperature, salinity, and pressure sensors based on fiber grating, the seawater salinity sensor based on multi-core fiber, and the interferometer based on Michelson and Mach-Zehnder. Seawater salinity and pressure sensors based on Fabry-Perot cavity, new optical fiber ocean temperature and salt depth sensor based on resonance and coupling technology, and fiber optic turbulence sensor based on two principles of heat and turbulent energy dissipation. This article analyzes the measurement methods and experimental results of various sensors and highlights the technical advantages and disadvantages. Finally, the development of optical fiber sensors in the field of physical ocean observation has prospects.