NZ Open Water & Secondary School Open Water Swimming Championships

A volcanic eruption 193,000 years ago blasted open twin explosion craters that now hold Lake Pupuke. The Freshwater Swim Fest & NZ Open Water Championships is an open water swimming race held across this enclosed volcanic basin in Auckland, New Zealand. Organized by Scott Rice and Quantum Events, who also founded the New Zealand Ocean Swim Series, the event brings open water racing away from coastal surf into a tranquil freshwater arena. The festival programme spans a broad spectrum of challenges, catering to sprinters, endurance athletes, and relay squads alike. Swimmers can choose distances starting at 100 meters, 250 meters, and 500 meters, stepping up through 1,000 meters, 2,000 meters, 2,500 meters, 5,000 meters, and 7,500 meters to the full 10,000-meter marathon.

Teammates can also combine efforts in a fast 4 x 500-meter relay race across the water. Adding a playful community dimension to the weekend, the festival hosts the New Zealand Doggy Swim Champs, an event where dogs swim alongside their owners on an off-lead 100-meter course. Staged in February during the warmth of late summer, the lake water generally registers between 20°C (68 °F) and 22°C (72 °F), creating comfortable non-wetsuit conditions for long stretches of continuous swimming. The lake course is marked out with clear sighting buoys and overseen by an attentive safety team, including qualified lifeguards from Surf Life Saving New Zealand keeping watch across every wave. Diving into the fresh water brings a buoyant, serene contrast to typical coastal chop, allowing competitors to lock into an uninterrupted rhythm.

Lake Pupuke: the drowned twin volcanic craters

Lake Pupuke plunges to a maximum depth of 57 meters, making it an unusually deep freshwater reservoir set right within suburban Auckland. Māori tradition explains this dramatic hollow through the legend of the god of earthquakes and volcanic eruptions, who destroyed a dwelling and left this gaping depression behind. Freshwater springs emerge along the ocean shoreline as natural freshwater springs, bubbling directly through the sand between Takapuna and Milford beaches. This volcanic origin links Lake Pupuke to the wider geology of Auckland's North Shore. About 3 kilometers away lies Tank Farm, another volcanic explosion crater that originated as a freshwater lake before rising sea levels after the last ice age breached its tuff rings and transformed it into a tidal lagoon.

That neighboring crater carries its own Māori lore involving the volcanic eruption of Matakamokamo, while its modern name recalls the bulk fuel storage tanks erected there during World War II. Further seaward stretches the Rangitoto Channel, an ancient valley of the Waitematā River during the Last Glacial Maximum that now serves as the only deep-water route for large ships approaching the Port of Auckland. Known in Ngāi Tai tradition as Te Awanui o Peretū after an ancestor who kept a parrot reserve on Rangitoto Island, the waterway was visited by the historic Tainui migratory canoe.

Takapuna Reef: the ancient fossil forest encased in basalt

Just about 1 kilometer from the race arena on Lake Pupuke, the story of the eruption continues along the saltwater coastline at the Takapuna Fossil Forest. When the Pupuke volcano erupted roughly 190,000 years ago, advancing basalt lava poured into an ancient coastal woodland, encasing the lower 1 to 2 meters of living tree trunks in stone shells. Over the past 7,000 years, natural coastal erosion gradually stripped away the softer rock layers, exposing these petrified hollow molds across the intertidal reef. Exploring this rocky foreshore reveals horizontal basalt logs aligned neatly towards the east-southeast, recording the exact direction taken by the molten lava stream as it surged seaward. Along the reef, visitors can examine natural lava arches created when the upper crust cooled and solidified while molten lava drained away beneath, as well as blister formations that swelled as trapped steam and hot gases rose from the burning vegetation.

The surrounding coastal landscape holds deep human roots as well. Directly north along the shoreline lies Milford Beach, historically named Onemaewao after supernatural beings from ancestral tales. Just north of the Wairau Creek mouth, a headland once protected the fortified Māori settlement of Wairoa Pā, before modern additions brought a sewage outlet at Black Rock in the mid-1920s and the Milford Marina in 1968. About 5 kilometers from the lake, the 12-hectare bushland reserve of Le Roys Bush preserves the valley historically known as Te Uruwao, where the Te Wai Manawa stream cascades over a high waterfall on its way toward Little Shoal Bay, a bay once used as a council rubbish dump during the 1970s.

About 7 kilometers down the coast stands North Head, a volcanic cone altered by marine erosion where the Tainui waka landed near Torpedo Bay and drank from a freshwater spring named Takapuna that later named the adjacent beach. Later reshaped by 25 years of convict labor into an extensive network of underground tunnels and gun batteries during the Russian scare of 1885, North Head defended the inner harbour alongside minefields and gun emplacements at Narrow Neck and Castor Bay before joining the Hauraki Gulf Maritime Park in 1972.

The Pupuke shoreline: Victorian pump houses and quiet waters

The immediate shoreline around Lake Pupuke offers a calm, civilized counterpoint to this turbulent geological and maritime history. In 1894, a brick pump house was constructed directly on the lake edge to draw fresh drinking water for local residents, functioning as the primary municipal supply until 1944. Rebuilt in 1906, that historic brick facility has since been transformed into the lakeside PumpHouse Theatre, complete with an open-air amphitheatre where audiences gather for stage performances right by the water. Today, the perimeter of the crater is bordered by established residential properties that look out across the sheltered inland basin. The lake bottom is dominated by beds of introduced Vallisneria plants that provide sheltering habitat for wildlife.

This lush aquatic vegetation supports a flourishing freshwater fishery, making the crater a popular venue for recreational anglers in pursuit of rainbow trout, tench, perch, rudd, and carp. For open water swimmers gliding between the buoys, Lake Pupuke delivers the rare sensation of navigating a secluded, historic volcanic basin right within the vibrant urban fabric of Auckland.