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 in 480 BCE.
According to Spartan military leader Pausanias (Description of Greece, 10.19.1.), prior to a critical naval battle with the Persians, Hydna and her father, Scyllis, volunteered to assist Greek forces by vandalizing the nearby Persian naval fleet. After defeating the Greeks at Thermopylae, Persian king Xerxes I had moored his ships off the coast of Mount Pelion to wait out a storm prior to the Battle of Salamis. Hydna was well-known in Greece as a skilled swimmer, having been trained by her father, a professional swim instructor, from a young age. She was known for her ability to swim long distances and dive deep into the ocean. On the night of the attack, father and daughter swam roughly ten miles through rough, choppy waters to reach the ships. They silently swam among the boats, using knives to cut the moorings and dragging away the submerged anchors. Without anchors and moorings to secure the ships, they crashed together in the stormy water. Most of the ships sustained considerable damage and a few sank. The resulting delay allowed the Greek navy more time to prepare and ultimately led to a victory for Greek forces at Salamis.
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. Pausanias tells us that "beside the statue of Gorgias is a votive offering of the Amphictyons towards father and daughter". It is thought that Roman emperor Nero plundered her statue and returned with it to Rome in the first century C.E.