Lake Karapiro Swim Fest

The deep, glass-flat reservoir of Lake Karapiro mirrors the emerald pasturelands of the Waikato Basin where international rowing champions train. This freshwater expanse in Cambridge, in the Waikato region of New Zealand, serves as the setting for the Lake Karapiro Swim Fest. Organized by the Ocean Swim Series, the gathering centers on an open 2.5-kilometre multi-lap circuit laid out along the protected lake waters. Swimmers can test themselves across an expansive roster of courses scheduled in April during the Southern Hemisphere autumn. The distance choices span 100, 200, and 500-metre sprints, expanding into endurance distances of 1, 2.5, 3.5, 5, 10, and an ultra-marathon challenge of 25 kilometres. Registration covers essential race equipment and trackside support for every competitor on the water.

Across the two-day festival, the water's edge stays energized by community activities and a live DJ playing music throughout the day. Staying close to the starting pontoon is straightforward, with campervan pitches and cabins located just a few hundred metres from the event base. The calm freshwater surface is occasionally colonized by hornwort, a submerged macrophyte native to North America that grows in dense aquatic beds. In addition, freshwater gold clams were first detected in Lake Karapiro in May 2023, prompting strict bio-security controls. Swimmers must complete a thorough wash of their wetsuits upon exiting the water at the dedicated cleaning stations, ensuring that gold clam larvae are not carried to other regional waterways.

Two days, eight distances: how the Swim Fest is laid out

The Lake Karāpiro Swim Fest packs its swims into two days and has the biggest line-up of swims in the NZ Ocean Swim Series. The Lake Karāpiro Swim Fest offers a 25 km individual swim, a 25 km relay, and swims of 10 km, 5 km, 3.5 km, 2.5 km, 1 km, 500 m and 200 m or 100 m. In the 25 km relay at Lake Karāpiro there is no set distance per swimmer, but each team member must complete at least one lap. The 25 km relay at Lake Karāpiro takes place at the same time as the 25 km individual event. Event host Dan Feisst of the NZ Ocean Swim Series predicted that the country’s only 25 km ultra-marathon swim would be the highlight of the Lake Karāpiro Swim Fest. The OceanKids swims at the Lake Karāpiro Swim Fest, over 100 m and 200 m, are for children aged 6 to 12.

Waikato River and the 1947 Karapiro reservoir

Lake Karapiro is a young body of water, created in 1947 by damming the Waikato River. The resulting impoundment feeds the Karapiro Power Station, which operates as the final hydroelectric installation along the entire length of the river cascade. When the river valley was flooded on April 4, 1947, rising waters permanently submerged the historic Horahora Power Station, turning former industrial machinery into an underwater relic. The creation of the lake also submerged older history along the sunken river corridor. Here lies the historic site of an 1830 battle, where fallen warriors were once cremated upon basalt river rocks that now rest under deep freshwater. Gliding over these calm waters, distance swimmers follow the historic line of the drowned river bed in total tranquility.

Maungatautari volcano and the ancient Moanatuatua peatland

Rolling green hills and native bush frame the lake basin under crisp rural air. Maungatautari is an extinct stratovolcano rising to an elevation of 797 metres roughly 14 kilometres from the race course. The mountain stands as an ancient natural landmark near Lake Karapiro, having formed roughly 1.8 million years ago. The surrounding plains, once covered by the vast Moanatuatua peat bog, underwent extensive nineteenth-century engineering to convert the ancient wetland into farmland. Between 1869 and 1870, laborers cut a primary central drainage channel through the bog to speed the evacuation of water. Over the following two decades, ditching efforts expanded rapidly, and by 1888 an astonishing 225 kilometres of drains had been excavated throughout the region to transform swampy terrain into pastoral grazing fields. In 1893, a visiting geologist recorded that the outflow from the main swamp drain had carved a canyon seventy feet deep where its runoff discharged into the Waikato River.

Mighty River Domain and Cambridge riverfront

Lake Karapiro hosts hydroplane racing as part of the annual New Zealand Grand Prix Circuit during the warmer months. Along the riverbank, the Te Awa walk and cycle way provides a direct route connecting the Mighty River Domain to the nearby town of Cambridge. Cambridge itself is perched on the picturesque banks of the Waikato River, about three kilometres down the watercourse from the race venue. To replace Cambridge's first bridge of 1870, a wooden truss girder crossing known as the Red Bridge was erected in 1876, located upstream from the 1870 crossing point. Roughly 500 metres upstream from Victoria Bridge stands the Fergusson Bridge, which spans the Waikato River on the exact river crossing site where the original 1870 bridge and the 1876 Red Bridge once stood.

As evening settles over the lake, swimmers can explore the waterways from a different perspective on guided kayak tours. Paddling at night brings you under areas glowing with constellations of native glowworms. It is an atmospheric conclusion to a weekend immersed in the waters and countryside of Lake Karapiro.