Swimming is still taking place at one of Te Whānau a Rangiwhakaahu's sites of significance.
Now, the hapū are making a stand to protect their treasure.
"Utilising rāhui is something our ancestors have done, used to protect the sanctity of our treasures," says Aperahama Edwards, chair of Te Whānau a Rangiwhakaahu.
Ecologists have identified new algae blooms at one of New Zealand's premier tourist destinations, Mermaid Pools. Local hapū, Te Whānau a Rangiwhakaahu have been told human waste is present in the water so a rāhui is needed.
"For the love of our treasure, but for the love of our people as well. Not just our own hapū exclusively - but this is a treasure for all" says Mr Edwards.
Locals here say that at its peak, more than 800 visitors come here a day to this site. A rāhui is also being placed on a former burial ground called Rangitapū Pā.
"It has been nothing but a fight to keep things on the right level" adds Jennifer McMath, a longtime resident of Matapōuri.
The Matapōuri hapū add that while the rāhui is in place they will collaborate with the Department of Conservation and other key stakeholders to ensure an enduring plan for the environmental, cultural and spiritual wellbeing on Te Wai o Te Taniwha
"Tell the world - let them know, this is a site of sacred significance. Think about it, protect it, look after it" says Ngapera Hohaia, of Kapa Kaitiaki.
Te Whānau a Rangiwhakaahu say that there is no time limit placed on how long the rāhui will be in place. However, it will be there for as long as it takes to restore the pristine condition of the water.
"If the hapū didn't take this stance to protect itself and these types of treasures - what would be left for future generations?" asks Edwards.
The rāhui will be formally applied to the area in the coming weeks.