Applications of aperture synthesis technique in a radar or sonar system can improve the resolution in the azimuthal direction. However, because of the existence of the vertical sound-speed profile in the ocean, the expressions for some parameters of sonar operation are not as simple as those of radar operation in the atmosphere. Important parameters such as the azimuthal resolution size and bounds of the pulse repetition frequency in the ocean environment are discussed. The method of ray tracing is used to find the formulations of those parameters. A numerical approach is then applied to solve the problem. Results show that the speed of sonar carrier motion must be low enough to find an operational range for the pulse repetition frequency.