The Epic Swim

The Epic Swim – Taupo is an open water swimming race held in the freshwater of Lake Taupō, in the Waikato region of New Zealand's North Island. Organized by the Ocean Swim Series, the event takes place across a weekend in midsummer January, taking full advantage of the southern hemisphere heat. The swimming schedule features an extensive slate of distances covering 100 m, 200 m, 500 m, 1,000 m, 2,500 m, 4,000 m, 5,000 m, 7,500 m, and 10,000 m. Ambitious endurance swimmers can take on the "Epic Epic", a multi-day challenge totaling 17.5 kilometres that combines the 10 km, 5 km, and 2.5 km races into a single weekend.

The competition course is mapped out over a 1.25-kilometre lap, turning the bay into an arena where spectators can follow the race continuously from shore. The event also hosts the NZ Masters 2.5km Swimming Championships, open to swimmers aged eighteen and over who belong to the NZ Masters Association. Race mornings on the lake commonly greet swimmers with glassy, crystal-clear water and crisp alpine air. In past editions, conditions on the water have ranged from mirror-smooth surfaces to light localized chop, with swimmers remarking on how the lake warmed pleasantly between race sessions.

The caldera of Lake Taupō: supervolcanoes and sunken valleys

Lake Taupō is the largest lake in New Zealand, occupying the central basin of the 350-kilometre Taupō Volcanic Zone that stretches from Mount Ruapehu in the southwest to the marine volcano of Whakaari in the northeast. Long before the modern lake formed, the ancient Lake Huka filled this rift valley to depths reaching 250 metres. That ancestral basin was erased roughly 25,500 years ago during the titanic Oruanui eruption of the Taupō Volcano, the most recent volcanic event on Earth to reach the maximum rating on the Volcanic Explosivity Index. A colossal freshwater basin now lies where the old rift valley once lay. Volcanic forces continued to reshape the lake perimeter, culminating around 232 CE with a massive eruption. The sheer volume of ejected pumice from that blast choked the lake's outlets, raising the water level so dramatically that it cut prominent wave terraces into the surrounding hillsides that still sit 34 metres above the modern waterline.

Horomatangi Reef and Mount Tauhara: underwater domes and taniwha legends

Beneath the surface of the lake lies a complex submerged topography shaped by the caldera's ongoing geothermal activity. In the heart of the lake rests the Horomatangi Reef, an underwater complex of rhyolitic lava domes where shallow volcanic shelves drop abruptly into submerged chasms plunging over 164 metres deep. Maori lore long associated this sunken reef with Horomatangi, a mythical water creature, or taniwha, believed to inhabit an underwater cave near Motutaiko Island. Mount Tauhara rises about eight kilometres from the race start. In Māori tradition, this solitary peak was a warrior who fled across the plateau after a battle, stopping in place on the shore as the dawn broke. Its summit provides a sweeping panorama of the entire caldera, tracing the vast expanses of water from the shore to the mountains.

The geothermal shores of Wairakei, Karapiti and Acacia Bay

The western flank of Tapuaeharuru Bay curves into Acacia Bay, where ancient volcanic promontories composed of lava more than 100,000 years old shelter the water from prevailing winds. Just four kilometres inland from the swim area lies the Craters of the Moon geothermal site, a 25-square-kilometre hydrothermal zone within the Wairakei field where volcanic heat escapes directly through the earth's crust. At the Karapiti Blowhole within the Wairakei field, vents release roaring pillars of steam so vast that nineteenth-century geologists recorded them from 20 kilometres away. For centuries, Māori navigators voyaging across Lake Taupō used this rising steam plume as a towering, natural beacon to steer their canoes back to shore.

The ground temperature around the thermal vents is so high that only specialized vegetation survives, including prostrate kānuka, tropical ferns, and rare mosses clinging to the heated soil. Bubbling mudpools form where sulfuric gases dissolve the bedrock, and thermal hot springs in the vicinity host resilient extremophile microorganisms adapted to thrive in scalding temperatures.

Where the Waikato leaves the lake: redoubts, falls, and trout

The outflow of Lake Taupō feeds the Waikato River. In 1870, an armed constabulary redoubt was erected on the riverbank to guard this strategic water crossing. That historic outpost was succeeded in 1941 by the control gates bridge, a major piece of civil engineering that regulates lake discharge to supply nine downstream hydroelectric power stations. Just north of town, the river surges through Huka Falls. In the 1890s, rainbow trout were introduced into Lake Taupō, quickly transforming the pristine waters of the lake and its feeder tributaries into an internationally renowned angling destination. For open water swimmers, this blend of deep caldera waters, ancient volcanic horizons, and alpine clarity makes slicing through the lake's calm morning surface a singular open water experience.