Meant to add, as much as I would like to believe, I pretty certain that Rama Setu is just another “Bimini highway” on a larger scale. Before sea level rise, it probably was used by humans; they may have even left their mark, but...
The southern basin of the Dead Sea is gone now (the water level has dropped), but in the 1950s it was still submerged, though shallow. The strait was ‘bridged’ by a submerged ridgeline, and there was (in the 1950s) some diving being done to search for the Cities of the Plain. There was evidence of a roadway, actual paved road, that had been built along that ridge at some long-ago time when the waters were lower as they are today.
The Giant’s Causeway is a natural volcanic formation that exists on the coasts of N Ireland and Scotland; it was attributed to Fingal (Finn, etc). I’m not sure the columns are continuous, if they aren’t that would be curious. I’d be surprised if stodgy old gradualists in the UK have ever researched that. :’)
https://en.wikipedia.org/wiki/Giant%27s_Causeway
http://www.google.com/search?q=giant%27s+causeway+in++scotland
http://www.google.com/search?q=Rama+Setu