internal wave in the Strait of Gibraltar

According to the mythology, it was Hercules, son of Zeus and Alcmene, who separated the two mountains, Calpe (Rock of Gibraltar) and Abila (Jebel Musa), formerly united as a single mountain range. Since then, these mountains are known as the pillars of Hercules, which pointed to the far end of the Mediterranean of the Greeks, the Non Plus Ultra, what the Romans wanted to mean that men should stop their expeditions there.