Poripori Water Holes are very popular with locals meaning it is likely there are a number of people at any one time. Pori Pori gets all day sun so the freshwater is relatively warm and the surrounding rocks make great places to lie on sun warmed rocks. There are various depths so check before entering the water or dive bombing.
When the siren sounds get out of the water immediately if you have not already checked Trustpower website. Trustpower releases water from the McLaren Falls Dam upstream of the PoriPori swimming hole over the summer months. There will be significant, rapid rise in water levels.