It's rated number five in the country's top 10 swim holes.

And it's raved about – 'the sweetest summer swim spot”, 'gushing fresh waterfalls” and a 'diamond in the rough” brags an online brochure.

Holly Clark at the popular swimming spot on Poripori Rd. Photo: Chris Callinan.

The pond with the big rep is the Poripori Rd waterhole at the foot of the Kaimai Range – it's chocka every weekend during summer with hundreds of cars and even more people.

But the Wairoa River which cradles this oasis has a dark and moody side and there are fears someone could die.

'It looks very harmless, but it changes from very harmless to very dangerous in a very short time,” warns a local, Graham Clark, from his own piece of paradise high above the river.

That's because every Sunday at 11am during summer, Trustpower floods the river for the adventure seekers – the rafters and the kayakers.

'And they release the dam at McLaren Falls so you and I can have electricity,” says Graham.

But it also means in just 20 minutes the river goes from a trickle to a torrent and the unwary and unfamiliar – who don't seem to see the warning signs, read the signs, or hear the siren – are vulnerable. Very vulnerable.

'I didn't hear the siren this week, or last week,” says Graham. 'Mind you it's noisy with the traffic on the bridge and the water.”

The vulnerable are the unwitting people who visit the area and cross the river to get to the famous waterhole and get caught.

One minute people are playfully negotiating stepping stones up to their calves on the way to the waterhole and the next it's ‘grade five' on the international white water rafting rapid system.

That means 'powerful rapids with very confused and broken water, violent and fast currents, abrupt turns, fast boiling eddies; with numerous obstacles in the main current.”

All that tells us 'a definite risk to personal safety” exists on the Wairoa River around the Poripori waterhole on Sundays.

Trustpower has been flooding the river on Sundays for years but for some reason people this summer are getting caught in 'life threatening situations”.

Graham and his wife Holly can vouch – they've had to make three rescues so far this summer.

One was a Hamilton family trapped midstream while crossing the river en route to the waterhole.

'The water got deeper and deeper,” says Holly. 'And around the stepping stones it quickly became rapids. The wife got washed downstream while the husband and two children struggled to the other side of the river.”

The wife became hysterical. 'She was screaming and crying and saying ‘my children, my children'. She thought her family had drowned.”

The family lost everything but the clothes they stood in. But the outcome could have been worse. 'The wife and mother swallowed a lot of water and was in a bad way. But it ended okay – they met up and hugged a lot.”

Then the Clarks had to dry the family and feed and clothe them, before driving halfway to Hamilton to pick up spare car keys.

They were happy to help but after the third rescue the Clark's decided the warning signs probably needed to be bigger, bolder and better and Graham alerted Trustpower.

When SunLive spoke to Trustpower, they agreed.

A bigger, double-sided sign warning with: ‘Water level rises from 10am on Sundays September through May' is being made and should be in place next week.

Another sign reading: ‘River levels may rise at any time because of hydro-electricity activity' will also be installed.

Both signs will also carry the international symbol for deep water.

Trustpower also points out that the river levels recede at 4pm on Sundays so people trapped when returning from the waterhole should wait.

In the meantime Graham says: ‘Beware!'. The Poripori Rd waterhole is 'amazing and idyllic but also dangerous”. These concerned and caring neighbours don't want a family outing to end with a funeral.