From the BBC link:
"The Indian Minister for Human Resources and ocean development said a group had been formed to oversee further studies in the area.
"We have to find out what happened then ... where and how this civilisation vanished," he said. "
Being fathoms under the sea must have made it very hard to carry on as usual...
But seriously, many climatologists think that the Earth's climate is unstable, and it can flip in and out of an ice age in a very short period. So if the last ice age ended over a period of mere decades, the sea level rise would have been difficult to keep up with.
Even today, most of the Earth's population lives near sea level, so a swift rise would not only flood cities and homes but disrupt trade and agriculture. It would be difficult to maintain law and order in circumstances where most people would be forced to become brutal survivalists just to get food and shelter. Education and all the 'higher things' we are so proud of would be unsustainable.