VERY possible. According to Plato, Atlantis was larger than Asia and Libya combined, so perhaps we are really dealing with a continent beneath the Earth -- under the Atlantic ocean to be precise. And if what the scientists are saying is true - in regards to there being ten times more water inside the Earth's mantle than the surface, then I can only imagine how huge the caverns are down there (possibly the size of continents). And who knows? Perhaps continents, themselves, are convex protrusions, which have an equally concave interior -- concave interiors filled with water?