Back when I was younger than I am now,(1995 or so) I remember Art Bell having this scientist lady on and they used a Side Sonar off the Coast of Cuba, saying it looked like anunderground city, blah blah blah, it was Sponsored by the LIFE Magazine or something too. Never heard what became of that.
It got hushed up because the aliens got all PO’d and threatened to make Cuba disappear! Couldn't allow any threat to the last bastion of the Revolution!
Or maybe there wasn't as much as they thought? Who knows!