In the legend of Jason and the Argonauts, the Symplegades are also known as the Clashing Islands.  The two rocky islands float on the surface of the water, and guard the entrance to the Euxine Sea (The Black Sea.)  The islands would crash together, crushing ships caught between them. A king that Jason had rescued told them how to get through- a dove was sent through first, and the islands crashed together, clipping the dove's tail. When the islands began to separate again, the crew of the Argo slipped through before they could close.  According to the legend, the islands became fixed in place after that day.

These islands were similar to the Planctae or wandering rocks, referred to in Homer's Odyssey.  They were also similar to the twin hazards ofScylla and Charybdis.

Pliny says the Symplegades are the Fanari Islands, and explains that "the story is due to the fact that they are separated by so small a gap that by persons entering the Black Sea directly facing them they were seen as two, and then when the line of sight became slightly oblique they gave the appearance of coming together." (Rackham, 1942.)