Observations and numerical models reveal the existence of the subsurface current in the opposite direction to the surface current off the Sri Lankan east coast. The undercurrent (200–1000 m layer) is most pronounced during the boreal spring and summer and transports more mass than the surface layer (0–200 m). Although the undercurrent is potentially a pathway of salt exchange between the Arabian Sea and the Bay of Bengal, the data and models suggest little salt transport by the undercurrent.