Atlantis was in fact minute; it could all sit on the head of a pin. Plato was playing with it in the bath one day and he lost it. Some say that it got wedged in his bellybutton, which explains a lot of Plato's navel-gazing in the latter part of his life. Others favour the safer assumption that it got washed away with the suds.

Since then, Greeks took up dredging the bottom of the Med regularly, in hopes of finding it, but all they could come up with was a lot of sponges and the odd amphora from older shipwrecks. So they kept using nets with ever smaller holes, till they damn near cleaned the Med out from fish. Still no Atlantis.

So the wisdom of the Ancients has effectively been lost. Which explains the stupid ways humanity behaves nowadays.