Over summer, a strange phenomenon plays out along New Zealand’s waterholes. Bridges, wharfs, cliffs and swimming pools throng with people readying to leap. Jumpers launch into the air, twist themselves into a v-shape – bums down, limbs akimbo – until they hit the surface, forcing water upwards in an almighty splash.

The bigger the splash and the more inventive the jump, the louder the cheers.

These are the “manu” jumpers – people who get a thrill and sometimes compete – in the sport of manu, a unique New Zealand diving technique similar to a bomb, developed by Māori and Pasifika communities, and which has now become a national pastime.

“It’s like an unspoken cultural rule in New Zealand – whenever you’re around water and there is something to jump off, you pop a manu,” says Nikita Hauraki, 26, who has been popping manus since she was a child.

“Everyone knows what a manu is, what it entails, how much hype is around it, even though not everyone has tried it out,” she says.

Manu jumper Pone Kahotea, 34, has been doing the sport in Tauranga, on the North Island’s east coast, since he was a kid.

“No matter where there are people swimming, there are people doing manus,” he says. Now, his 12-year-old, Bayley, is perfecting his technique.

“Kids will go hard all day,” Kahotea says. “These young kids have made up their own styles and redefined it – they’re crazy and much better than we were.”

The aim of a manu is to create the highest splash and while the v-shape is the most common technique, other styles including the coffin (feet first, straight body), the gorilla (head and shoulders first), and the staple (hands and feet first) regularly feature.

“If someone’s done a really good manu, where the splash is almost in a shape of a tree trunk, and it goes straight up … and obviously high, it is considered a really good [one],” says Elisha Rolleston, 32, whose ability has earned him the title “Manu King” in his home region of Tauranga.

“Nowadays, we’re starting to see different styles of the manu … like the tailwhip – you jump out and swing your legs to the side, it looks like a breakdancing move in the air.”

No one is entirely sure where, or how, the manu evolved. Some believe it emerged in the 1990s at the outdoor Moana-Nui-a-Kiwa pools in the South Auckland suburb Māngere, while other regions claim it evolved at their local bridges decades earlier. The name manu – meaning bird in the Māori language – also has a murky history. Some think it references the act of flying into the water, others believe it is a shortened version of Māngere.

What is certain, is the art of the manu emerged within Māori and Pasifika communities – something Rolleston believes is linked to these communities’ strong connection with water. “There’s a real sense of community – people swimming, having a good time,” he says.

Visiting local waterholes was also a cheaper option for those on lower incomes, he says. During his years living in Tauranga and the neighbouring inland region Waikato, Rolleston said European New Zealanders tended to avoid local rivers and waterholes, in favour for the beach.

“But at wharfs and bridges, Māori are the majority – it was probably more feasible option to take [families] there for a swim all day,” Rolleston says.

The pastime – which has always had a competitive edge – now has a formal annual championship: the Manu World Champs. Competitors attend heats around the country over summer, in the hopes of diving at the grand final held on Auckland’s waterfront in March.

The professional competition may be boosting the profile of manu jumping, Rolleston says, but it will always remain a curious, fun and free sport.

“Doing the manu is something within our DNA as New Zealanders – it’s certainly unique to us and we are proud of it.”