Using a ray tracing model, acoustic propagation through a subsurface eddy is investigated. The eddy with a 460 km diameter lies at approximately 23° N, 126° E. The presence of the subsurface eddy is found to result in significant alterations to the received acoustic field. Affected by the subsurface eddy, the location of a given convergence zone can be different from usual with optimum propagation conditions. For a source deployed outside of the eddy, the subsurface eddy creates a surface duct by modifying the sonic layer depth. A maximum of 15 km difference in the range of a given convergence zone is found between the propagations with the presence and absence of the eddy when the source is placed around 100 m depth. However, for a source within the eddy, the intense shift in convergence zone patterns occurs only when the source is deployed around 300 m depth. These ocean-acoustic results can provide essential information for operating technologies such as communication devices, underwater sonar, and navigation systems.