Consultants are on the job to help save the waterway, which has been suffering from an algal bloom and coral bleaching.
Despite its problems, Muri is still one of the Cook Islands' biggest drawcards for tourists and several were out paddling, snorkelling and lolling in the warm shallows last week.
"It's a peaceful lagoon and I'm not too strong in the water so it's about my speed and it's sheltered and you can snorkel right off the beach. This is perfect for us," said Richard Smith, who had just arrived from Canada.
