A recent scientific expedition to the remote Western Islands has revealed coral reef systems of exceptional health, with researchers ranking the location among the most pristine marine environments globally.

An eagle ray silhouetted. | PS PNG Expedition Leg 2, Hermit Islands

The survey, led by Jenn Caselle of Pristine Seas Papua New Guinea, spent three days assessing the region’s habitats. According to the expedition team, the density and diversity of marine life in the shallow waters exceeded expectations, prompting veteran divers to describe the reefs as some of the best they have ever documented.

Evidence of fishing can be found even in the most remote parts of the world. | PS PNG Expedition Leg 2, Hermit Islands

“The coral reef survey team agreed that these reefs were among the best coral reef locations we have ever visited,” said Caselle, the expedition’s Science Lead. “And collectively, we have surveyed a lot of amazing locations around the world.”

While the team noted that deep-sea habitats in the area appeared quieter than anticipated, the shallow coral reefs offered a stark contrast, teeming with activity. The volume of marine life was so compelling that the research team opted to forego breaks, remaining in the water for extended periods to maximize data collection.

Underwater cinematographer Dan Beecham surrounded by fish. | PS PNG Expedition Leg 2, Hermit Islands| PS PNG Expedition Leg 2, Hermit Islands

In a single six-hour window, the team documented significant numbers of apex predators and megafauna, including:

• Shark Populations: A localized migration of 28 Blacktip reef sharks moving from the shallow lagoon to offshore reefs, alongside a nursery of 32 juvenile gray reef sharks patrolling a wall.
• Large Fish: Sightings included 10 large Bumphead parrotfish, a species often indicative of reef health.
• Interspecies Interaction: Dolphins were observed hunting cooperatively with two massive giant trevally.

Fish above a plate coral. | PS PNG Expedition Leg 2, Hermit Islands

Caselle noted a rare behavioral event where dolphins approached the divers closely during fish counts, a deviation from the animals’ typical avoidance of scuba bubbles.

The expedition highlights the critical role of Indigenous stewardship in conservation. The pristine nature of the ecosystem is attributed to the local community’s management of their waters.

The science team worked in close collaboration with Ben, a local guide and conservationist who coordinates community protection efforts.

A group of feeding manta rays barrel roll. | PS PNG Expedition Leg 2, Luf, Hermit Islands

“These islands are a special place, and the community members made our visit extra special,” Caselle reported. “They know their reefs well and are set up to guide visiting scientists.”

For the Pristine Seas team, the Western Islands provide a vital baseline for what healthy coral ecosystems should look like.

A pair of gobies wait outside their sand hole. | PS PNG Expedition Leg 2, Harangan, western Manus

“All of these animals can still be seen on reefs throughout the world, but to see them all together in one day is a treat,” Caselle said. “Today, I feel inspired and hopeful. That hope motivates us to do the work that we do.”