Te Arawa Lakes Trust chairman says a floating wetland launched early last year in Lake Rotoehu near Rotorua, is already starting to have a beneficial effect.
The wetland is made up of more than 350,000 plastic soft drink bottles each growing a wetland plant.
It's the first time in New Zealand a floating wetland has been used to try and restore water quality in a lake which is nutrient enriched and has abundant algal growth.
Toby Curtis says it's visually very obvious the water around the wetland is in much better condition than it used to be.
He says the lake is cleaner and clearer which are good signs that water quality is improving.
Mr Curtis says the Rotorua Lakes Strategic group which includes the trust, the district council and the Bay of Plenty Regional Council is delighted.
He says two smaller floating wetlands in a sulphur infected part of Lake Rotorua near Ohinemutu, are also proving their worth.