Looking out now over the Indian Ocean from Mnemba Island, it is hard to believe that just three years ago the stunning coral reef surrounding this part of Tanzania’s Zanzibar archipelago was dying.
Under threat from climate change, overfishing and other human activity, the islanders faced losing their livelihoods and the prospect of moving away altogether.
Anxious to save the colourful, oval-shaped reef that is fairly close to the shore and around 7km (4.3 miles) in length, communities on the small island have embraced a conservation project which has managed to restore some of what has been lost.
The initiative also aims in other ways to protect the reef, which is known around the world for its beauty.
The water is so clear that the reef, which lies 10m (32ft) below the surface, seems almost within touching distance.
But a few years ago locals began to notice how stressed the coral was looking - part of this was due to the changing climate, which has brought warmer sea temperatures.
Coral may look like a plant, but it is a kind of animal - in fact multiple tiny creatures called polyps. They grow very slowly and make a hard outer shell by extracting salt from seawater, then fuse together to make what are called colonies.
Reefs are sometimes referred to as the "rainforests of the sea” because they create ecosystems that support a diverse range of marine life.
But when the water heats up by a few degrees more than normal it causes the coral to drive out the brightly coloured algae that live within and provide nutrients. As the algae leave, the coral fades, becomes bleached and eventually dies.
Dynamite being used by fishermen has also been killing off the coral, as well as the volume of unregulated tourist boats and divers causing damage to the reef.
Mnemba Island fishmonger Juma Mshindan says it became clear something was very wrong: “There is a significant difference in the availability of fish before compared to now. In the past, fish were plentiful.” The sustainable tourism group &Beyond and non-profit organisation Africa Foundation began collaborating with islanders in September 2021 to help address some of these issues.
Underwater nurseries were created using steel-mesh tables, where coral fragments are grown to be replanted on the coral reef.
They are tended and nurtured by local divers who have been trained as conservation rangers.
It takes about two or three months for a coral colony to form and then the rangers take them to the reef.
The results so far are encouraging, with 80% coverage restored on what is called the “house reef” which surrounds the island.
"It’s like they have grown by themselves,” says conservation ranger Hija Uledi.
“We have restored the reef, and you can't tell the difference. Now they have fish around. The work is great, and many species can be seen.”
The conservationists also created artificial reefs - steel and stone structures which were placed about 3km off the island and where the conservation rangers also plant newly grown coral from the nurseries.
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