XTERRA Greece O.W.S. Challenge 10K Open Water Swim

The XTERRA Greece O.W.S. Challenge 10K Open Water Swim is a long-distance sea competition staged along the coast of Voula in Attica, Greece. Organized jointly by the Municipality of Vari-Voula-Vouliagmeni and TRIMORE - XTERRA Greece - ISOMAN Hellas, the event brings open water swimmers together on the sands of A' Voula Beach. The challenge first launched along this coastline in 2013 and previously visited Vouliagmeni and Varkiza before establishing its permanent home in Voula. Held in autumn during October, the gathering welcomes athletes from the age of fourteen to ATHINES By The Sea, which operates as the lively race village right on the waterfront. The event caters to multiple aspirations with courses over 200 meters, 1 kilometer, 2.5 kilometers, 5 kilometers, and a premier 10-kilometer distance.

From the starting arch on the beach, the racing corridor guides swimmers out perpendicular to the shore into the open bay. The morning swell and shifting currents test each participant's pacing as they settle into a steady rhythm. Those taking on the 5-kilometer and 10-kilometer courses break away from the nearshore lanes to swim out and around the island of Ydrousa. For swimmers on the 10-kilometer route, the course requires completing two full laps of this outer circuit. A strict cutoff requires swimmers to finish their opening lap before late morning to stay in the race. Wetsuit use is dictated by the water conditions: neoprene becomes mandatory when the sea drops below the thermal threshold, and is prohibited when the water stays warm.

The Voula race: Ydrousa laps, the buoy door, wetsuit limits

The Municipality of Vari-Voula-Vouliagmeni and TRIMORE announce the 2026 swim as the 13th XTERRA O.W.S. Challenge. At the ninth XTERRA O.W.S. Challenge, the first held at the ATHINES By The Sea beach, the races included for the first time a circuit of the islet of Ydrousa, which lies opposite the beach. At that ninth edition a team of kayak guides accompanied the swimmers on all the routes. In front of the beach, swimmers pass through a door of two buoys 40 meters apart, then swim outside the buoys of their distance. Swimmers on the 5k and 10k can drink water on arrival at the island of Ydrousa, and those on the 10k can drink again between the first and second laps. A wetsuit is mandatory if the sea temperature is below 18 °C (64 °F) and prohibited above 24 °C (75 °F); swimmers in wetsuits are ranked separately from the others.

Ydrousa islet, the wild reef opposite Voula

Rounding Hydrousa puts marathon swimmers into deep, exposed water less than a nautical mile off the mainland. The islet sits exactly 0.7 nautical miles from the coast of Vari-Voula-Vouliagmeni, covering an area of nearly fifty-seven thousand square meters. Out on this perimeter, the sound of the shoreline fades into the steady splash of your stroke and the rolling chop of the gulf. In the nineteenth century, the barren island was leased out to local shepherds who ferried their livestock across from the Attica coast. Tucked into the island's rock face is a World War II shelter complex. The subterranean bunker contains tunnels, defensive corridors, and supply storage rooms, leading out to a concealed underground balcony that looks across the open waters of the Saronic Gulf. Down beneath these wartime cliffs, divers have actively worked to protect the marine environment. In a past ecological initiative, volunteer divers cleaned the seabed around Ydrousa by hauling up twenty-six large tires, leaving clearer water.

Lake Vouliagmeni and its sunken cave system

Lake Vouliagmeni provides a dramatic contrast to the open sea of the bay. This flooded geological wonder formed roughly two thousand years ago when an earthquake caused the stone ceiling of an enormous cavern to collapse. The resulting lake is fed by underground currents originating on Mount Hymettus as well as warm seawater that filters through submerged rock chambers. A freshwater spring steadily tempers the water, keeping its salinity at a mild, brackish level. Beneath its sheer rock walls lies an extensive underwater cave system that remains only partially explored despite numerous diving expeditions. Any sense of trepidation disappears upon entering the basin, where the water maintains a gentle, comfortable warmth year-round and never falls to winter chill. Rich in hydrogen sulphide, the lake has served as a therapeutic spa since the end of the nineteenth century.

Cape Colias and the Salamis battle debris

Cape Colias is the ancient promontory known today as Cape Agios Kosmas. Following the Battle of Salamis in 480 BC, the wreckage of the defeated Persian fleet washed onto Cape Colias. The Athenian maritime victory was remembered across Attica, and a captured enemy trireme was later dedicated to Poseidon at Sounion. Even before the Persian Wars, the shoreline here was shaped by naval cunning when Solon used a tactical beach ambush at Colias to defeat invading Megarians arriving by sea. In classical times, travelers visited a coastal sanctuary on the cape dedicated to Aphrodite Colias and the Genetyllides. The headland was also prized for deposits of exceptional clay, which potters mined to fashion fine Athenian ceramics. Breathing in the sea spray on race morning connects you to waters where ancient ships and coastwise sailors have navigated for thousands of years.

Cape Zoster and the ancient road at Kavouri

Cape Zoster juts into the gulf, forming an ancient landmark situated between the classical settlements of Aexone and Anagyrous. Sheltered within the grounds of the Astir Hotel beach stands the Temple of Apollo Zoster. The peninsula of Kavouri reaches twelve hundred meters out into the sea, measuring four hundred meters wide and terminating in a headland forty meters high. Along the sheltered side of the peninsula, Megalo Kavouri beach offers nine hundred meters of shallow, clear sea and a small islet that can be reached on foot. Running beside the shore is an ancient road discovered near the sand, spanning three hundred meters in length and reaching up to six meters in width.