Reef "Leftheris" or "Myrminx"

On the reef called Myrminx or Lefteris, in the narrows between the west coast of Skiathos and the east coast of Pelion, one can see the remains of a stone column. It has been conjectured that this may have been a memorial put up by the Persians to commemorate an engagement between three Greek ships and ten of their own. Another school of thoughts (Lykoudis) holds that it was some kind of seamark, possibly even a lighthouse, built by Xerxes' expeditionary force. If the second theory is correct, it makes this the oldest seamark in the world, since it predates the Pharos at Alexandria by about two hundred years.