Tamilians find some ruins underneath the sea, immediately jumps to the conlcusion that it is 15,000 years old thinking this will finally Kumari Kandam existed

The seventh redevelopment was probably about 2,500 years ago and it might have submerged due to rise in sea level about 1,020 years ago.

I assume there's some reason they're assuming its the seventh, that puts an urban complex in the Tamil heartlands as far back as the IVC which would be pretty revolutionary.

Though tbh I've always suspected there's more to the Tamil's origins than we know right now. There's no real reason for them to have been as good mariners as they were from the earliest historical period, if you sail out from Tamil Nadu you have to hug the coast and most of the Eastern coastline only becomes civilized in the Classical Age, so nothing decent there. If they were primitive sailors they'd presumably colonize Sri Lanka but they didn't do this either. Gujjews, I could understand them being good mariners in the Bronze Age cause you have Mesopotamia, Egypt all within reach. So IVC port cities in Gujjewstan aren't surprising. But a major port city in Tamil Nadu especially if its unlinked to Arabian sea trading complex would mean the existence of significant civilization there as well as further East, probably in the sunken portions of SEA.

This is entirely headcannon but people used to associate Dravidians with southern Iraqis(Elam) of the Bronze Age and there's some weird similarities between Tamil and Japanese languages. I imagine both ethnicities living in the former SEA and migrating west and east respectively as sea levels rose. That'd explain weird communities like Brahuis neatly too, splinter communities as the mass moved West hugging the coast.