TACKLING A GLOBAL THREAT BENEATH THE SURFACE – BROOK MCRAE
Brook McRae has spent most of his life in or around the water – not only as a diver and entrepreneur, but also as a passionate guardian of the ocean’s future.
Words Sam Mickell
Based in Mahurangi West on a lifestyle block with his wife Sarah, two daughters Frankie and Coco, and a small collection of animals, Brook is a serial entrepreneur with a long- standing commitment to marine conservation. He and Sarah previously launched the Clearyak business at Goat Island Marine Reserve – a fleet of see-through kayaks offering visitors a unique window into New Zealand’s underwater world.
Ten years ago, Brook founded Commercial Dive Specialists (CDS), a Mahurangi- based company that has become a national leader in underwater construction, marine engineering, and biosecurity. His work has taken him across New Zealand and Southeast Asia, including high-risk assignments like body recovery and explosive weapon surveys inside a sunken naval submarine in India.
More recently, Brook has turned his attention to a different kind of threat: Caulerpa, a fast- spreading invasive seaweed wreaking havoc on marine ecosystems throughout Aotearoa. First detected off Aotea Great Barrier Island, it has now taken hold in over 1500 hectares across Mercury Island, Waiheke, Kawau, and the Bay of Islands. Caulerpa smothers native seagrasses, starves shellfish and fish of oxygen and habitat, and threatens the survival of iconic species like scallops and snapper.
“We first encountered Caulerpa during marine biosecurity work four years ago,” Brook explains.
“Even then it was spreading fast. I realised quickly how serious it was – not just as a diver, but as a father thinking about the future of the Hauraki Gulf for my daughters.”
Determined to act, Brook and the CDS team invented a groundbreaking solution called Rehabitat. In simple terms, it’s a mobile floating chamber that can be lowered onto the seabed to kill Caulerpa without harming the surrounding marine environment. It works by pumping a controlled dose of chlorinated water into the enclosed area, killing the invasive seaweed, then extracting the chlorine before releasing the water back into the ocean.
“It’s like a pop-up treatment pod for the ocean floor,” Brook says. “It uses far less chlorine than other methods and ensures nothing escapes. The seabed bounces back quickly and we’re seeing great results in early trials.”
Initially self-funded, the project was selected last year as part of a $10 million Ministry for Primary Industries (MPI) innovation fund to fight marine pests. CDS was one of only three companies chosen and is the only one using this sealed chamber technology. Trials in the Bay of Islands are currently underway, with promising results and strong potential for national use – or even adaptation for other marine threats.
As a long-time Mahurangi West resident, Brook says the local coastline has always held a special place in his heart. “This community is surrounded by ocean – it’s a part of our everyday life, whether you’re diving, fishing, or just taking your kids to the beach,” he says. “That’s why we’re doing this work right here. We want to protect what makes this place so special.”
While the invention is innovative, Brook’s motivation remains personal. “I want my daughters and their generation to grow up exploring the same rich, thriving ocean I did. That’s what this is about.”
With deep roots in Mahurangi and a vision for marine protection on a national scale, Brook McRae, alongside his team at Commercial Dive Specialists, is proving that innovation, when guided by purpose, can start small and ripple out to make a global impact.