Nagapattinam Coastal Security Group DSP Sivasankaran said a fisherman found the objects this morning and immediately alerted the CSG police.
CSG officials got in touch with the Coast Guard and the naval detachment at Thopputhurai in Vedaranyam.
The two objects, measuring four feet in length and cylindrical in shape, were taken to the naval detachment and examined by experts.
It was later found that the objects were actually sonobuoys, which are used by the Defence forces to transmit acoustic information, Sivasankaran said.
Sonobuoys contain sensors and communication equipment thattransmit acoustic information to the aircraft from which they were deployed.
The sonobuoys have now been kept at the naval detachment and further investigation is on, the official added.