Wikipedia
Hydna of Scione (alternately called Cyana) ( fl. 480 BCE) was an ancient Greek swimmer and diver given credit for the destruction of the Persian navy around 480 BCE.
According to Pausanias ( Description of Greece, 10.19.1.), during a critical battle with the Persians Hydna and her father volunteered to help in the war. Hydna trained by her father, Scyllis of Scione, who, tradition says, dived into the very deepest parts of every sea, had played in ocean since infancy. As an expert swimmer, he taught his daughter Hydna to dive well into the deepest parts of the sea. When the fleet of Xerxes was attacked by a violent storm off Mount Pelion, father and daughter completed its destruction by dragging away under the sea the anchors and any other security the triremes had. Together, they swam through some ten miles of choppy, storm-tossed waters to where the Persian navy was moored for the night. Knives in hand, they silently swam among the boats, cutting their moorings. Tossed about by the wind and waves, the ships crashed together; some sank; most were crippled. And so battle was avoided for the time being.
In gratitude for the heroism shown by Hydna and her Father, the Amphictyons dedicated statues to them at Delphi, the most sacred site of the Greek world. Beside the Gorgias is a votive offering of the Amphictyons towards father and daughter.