The reef development here is no accident. For generations, local fishermen have safeguarded their supplies of fish by creating marine protected areas. Communities would agree on the boundaries, mark them off and ban fishing there: no nets being dragged around, no rumbling boat motors. In these areas, fish and coral develop untouched, so future generations have a chance to fish them.

In 2016, the East Timorese government started putting these practices into law. It created a budget and started paying rangers to help out. But the budget is minuscule and barely covers the enforcers’ salaries.

Accordingly, much of the day-to-day work around the reefs has remained with the fishing communities.

Inside a concrete shack to protect from the hot midday sun, Ms. Dale gathered a group of local fishermen and hotel owners together with Compass Diving, based in Dili, to share ideas for eco-tourism.

Their pristine reef, she explained, could bring in divers from around the world who would pay good money to explore them. The fishermen sat smoking cigarettes with their arms guardedly crossed.

“We don’t know where to start,” said Lucas Monteioro, 32, a jobless resident of Com. “The community is interested in tourism and making new money, but people here only have the sea.”