Eyes fixed ahead, the gardener delicately held the spiky-sharp thorn in her gloved hands. It was capable of giving her a deep cut, so she had to be careful. Occasionally, she paused to take a deep breath, but otherwise she didn’t talk and was focussed on tending to the Eden-like garden in front of her. Bowed on her knees, she zip-tied the thorn to another plant, before showing her two companions how to tie and transplant another fractured branch. If it weren’t for the tropical fish darting around their cumbersome scuba gear, you’d swear they were tending a shrubbery.

This is how they do the gardening, Maldives-style. While most travellers visit the Indian Ocean’s string of coral-fringed islands and coconut palm-topped atolls for their pearl-white sandbanks, cyan waters and promise of never-ending romance, it is the iridescent, rainbow-coloured coral reefs below the surface that are the real stunner.

Back in 1998, the Maldives’ corals were hit by El Niño, a periodic weather phenomenon that marine biologists believe killed 90% of the country’s reefs. With just a 1C rise in temperature, corals turn white, exposing their inner skeletons and making them increasingly vulnerable – but Maldivian waters increased by a catastrophic 4C. Recovery was then hampered by the devastating 2004 Boxing Day tsunami that smashed into the chain of coral reefs, leaving hundreds almost beyond repair.

In the 75-strong island cluster of the Baa Atoll, a 35-minute seaplane flight from the capital Malé, you will find a greater diversity of fish than in most marine parks. Kihavah Huravalhi, home to the luxurious Anantara Kihavah resort, is one of the atoll’s few inhabited islands, and coral adoption and reforestation is flourishing here. On a morning dive or snorkel, it is possible to see a number of upside-down nursery frames, made from up-cycled flower baskets and metal rods, which house fractured pieces of coral.

The coral adoption and reforestation initiative has great ecological value as it involves replanting reef fragments to accelerate the regeneration of coral growth in the Maldives’ reef-fringed atolls. Within a year of planting, faster growing acropora corals, such as stag horn and table corals, completely cover the structures, while slower growing species such as sun corals are introduced once the colonies are well established. At this point, fragments are then either painstakingly transplanted onto new structures – similar to piecing together a gigantic organic jigsaw – or relocated back onto the natural reef where they can thrive.

So how effective can underwater gardening be? “It’s definitely progress, and that’s all we can ask for,” said Evelyn Chavent, Anantara’s resident underwater expert and one of only six marine biologists permanently based in the Baa Atoll. “You’d be surprised by how quickly some of the corals grow – up to 2.5cm per year – so it’s a fast learner.”

There are some 450 different species of coral here, and not every species has a fighting chance, but coral reforestation and adoption programmes help educate local fishermen, school children and tourists, who can adopt their own coral frames  and monitor the coral’s growth online. To underline the country’s eco credentials, the Maldives is also on track to become the world’s first carbon neutral country by 2019 – something sceptics believe is overly ambitious. But scientists say action is essential because rising sea levels could engulf the country.

Kihavah may be one of the Maldives most popular places for underwater gardening, but it’s far from the only option for lessons in the marine world. Located in the same atoll, Dusit Thani resortoffers underwater education with a marine biologist, and guests can adopt a spotted eagle ray to help long-term conservation of the vulnerable species. At the Four Seasons Resort Maldives at Landaa Giraavaru, the coral propagation project has to date transplanted more than 120,000 fragments of coral – one of the most successful reforestation projects in the world. The islands of Dhigu, Veli and Naladhu in the South Male Atoll, also run by the Anantara hotel group, are home to a number of coral adoption projects. Naladhu, in particular, sits on a crisp clear azure lagoon sheltered by a house reef that attracts black-tipped reef sharks and a huge variety of smaller species, including parrot and clown fish.

So what does it feel like to go gardening underwater? According to Chavent, it is something that will stay with you for life. “In years to come, some guests will come back to find that the small piece of coral that they planted has flourished and created a whole miniature eco-system around it,” she said. “That kind of sustainable tourism is priceless.”