Editor’s note: Below is an excerpt from a Special Report on the Lau Seascape in Fiji. It was originally published on June 7, 2017.

Last month, a team of conservationists set sail from the island of Fiji. Their mission: to survey marine life in the Lau Islands, an unheralded group of islets scattered over thousands of square miles of the South Pacific.

They were seeking out species — but also clues to the health of these little-explored waters. With warming seas wreaking havoc on coral reefs and upending fish migrations throughout the Pacific, managing this area will be crucial for ensuring its resilience to climate change — and ensuring that it can continue to provide food and livelihoods for the thousands who call the Lau Islands home. (Read the first story in this series here.)

In this report, Edgardo Ochoa, marine safety officer at Conservation International, recounts the resplendence and the risks of daily dives in remote waters — as well as some of the unfortunate finds he came across in the deep.

When I came across the fishing line, I knew immediately what it was — the material, the thickness, the size. My air was low, but I needed to at least try to retrieve it, or it would remain tangled in the reef. To roll up the lines, I have a specific technique to protect myself from the fishing hooks: wrapping the line in on itself and making several large bundles to gather as much as the line as possible (see video above). In this case, the section I retrieved was 500 meters (1,600 feet) long.

Five hundred meters that some commercial fishing boat cut off and left in this pristine coral…