The Symplegades were said to be in the strait between the Aegean and the Black Sea (known to the ancient Greeks as the Euxine).
Symplegades (sim-PLEG-uh-deez). The Clashing Rocks, which smashed together upon any ship passing between them. Jason and the Argonauts had been advised to avoid this trap by causing a bird to fly ahead of their vessel. The Symplegades clashed together on its tail feathers, then drew apart in readiness to clash again. At this moment, the Argonauts sailed through safely, with only minor damage to the very stern of their ship.

The Symplegades were said to be in the strait between the Aegean and the Black Sea (known to the ancient Greeks as the Euxine).
Symplegades (sim-PLEG-uh-deez). The Clashing Rocks, which smashed together upon any ship passing between them. Jason and the Argonauts had been advised to avoid this trap by causing a bird to fly ahead of their vessel. The Symplegades clashed together on its tail feathers, then drew apart in readiness to clash again. At this moment, the Argonauts sailed through safely, with only minor damage to the very stern of their ship.