Ancient Underwater Structure off the coast of Malibu?

 An interesting anomaly off the Malibu coast in California, reported back in 2014 by ABC News as a potential Alien base, and perhaps it is an ancient structure? 
Located on Google earth (coordinates 34° 1’23.31″N 118° 59’45.64″W). It is 3 miles wide and found under 2000 feet of water, what do you guys think about this? natural or manmade formation?