Ocean Swim Series - Lake Karapiro

Lake Karāpiro offers a unique environment where the water is shaped by the precise operations of the Karāpiro Power Station. This facility manages a constant flow of 148 cubic metres per second through three Kaplan turbines, a movement that provides a steady, controlled current for swimmers. While you navigate the course, you are essentially tracing the path of the Waikato River, which was dramatically altered in April 1947 when the dam was first filled. This filling process resulted in the total submergence of the former ten-megawatt Horahora Power Station, which now rests 13 km upstream from the current dam, hidden beneath the surface you traverse.

## A landscape beneath the surface

Beyond the engineering history, the lake floor holds memories of the 1830 Battle of Taumatawīwī. This significant conflict between the Ngāti Hauā and Ngāti Maru tribes took place just two kilometres south of the current Karāpiro Domain. The site of the battle and the subsequent cremation of warriors on river rocks were lost to the rising waters, giving the lake its name: 'karā' for basaltic stone and 'piro' for the foul-smelling remains of the funeral fires. As you swim, you are moving over a site of deep cultural significance and long-standing history. Today, the venue is widely recognized by the International Rowing Federation as one of the world's fairest and most picturesque courses, having hosted the 1978 and 2010 World Rowing Championships.

## Race day logistics

The event program spans two days, offering distances ranging from 500m to 25km. Registration fees vary from free for the OceanKids events to 345 NZD for the longest individual challenges. All participants are required to respect local biosecurity measures due to the presence of invasive gold clams, which were first detected here in May 2023. Because these organisms can rapidly dominate lakebeds and alter nutrient levels, you must clean your wetsuit thoroughly after exiting the water to prevent their spread to other ecosystems. Support is central to the event, with the 2.5km multi-lap course designed specifically to keep swimmers within sight of spectators and safety personnel. Whether you are aiming for a personal best or participating in the 25km relay, the focus remains on a well-supported, spectator-friendly experience in the heart of the Waikato.