secondly, as i have pointed in my previous (big) posting, east coast of tamil nadu shows a clear land-level-rise and sea fossils have been discovered at an inner location on the land, and to your interes it is not far away from poompuhar. the entire east coast has been rising becuase of many factors one of them is sedimentation which has been becoming at an incerased rate becuase of a reverse process happeneing at the Gangetic delta (for sedimentation to happen there should be erosion at another place). not only the erosion at gangetice delta (West bengal of India and Bangladesh), the sea currents, seismic activities of the region, erosion elsewhere (may be near the indonesian isalnds, as the "sunda land has also been submerged"). it is not such a simple equation that so many meter of depth at a distance of so many meteres from the shore means this year!!!!
a good analysis of as many factors as we know is required before jumping to any conlcusion.