RAROTONGA - Divers clutch wooden spears as they plunge beneath the waves, hunting hordes of hungry starfish destroying the coral reefs around the Cook Islands.
These makeshift tools are their best weapons in the war against crown-of-thorns starfish, a coral-munching species eating through tropical reefs already weakened by climate change.
The Cook Islands, a South Pacific nation of about 17,000 people, is in the grips of a years-long outbreak, says marine biologist Teina Rongo.
"It can completely kill off the entire reef, right around the island," said Rongo, who organises volunteers protecting the reefs fringing the isle of Rarotonga.
"I think there seems to be a Pacific-wide outbreak at the moment, because we're hearing other countries are facing similar challenges."
A single crown-of-thorns adult can eat more than 10 square metres of reef each year, squeezing its stomach through its mouth to coat coral in digestive juices.
They pose a major threat to Australia's Great Barrier Reef, where scientists have developed robots that hunt down the prickly invertebrates and inject them with poison.
"At the moment, you basically kill them by injection," said researcher Sven Uthicke, from the Australian Institute of Marine Science.
"It could be vinegar, it could be lime juice or ox bile.
"Others are building chemical attraction traps. It's all very promising -- but it's in the development stage."
Rongo finds it quickest to pry the feasting starfish loose using a wooden stick cut from the dense timber of the Pacific Ironwood tree.
"Basically, we use a stick with a hook at the end," he said.
"We've made some modifications over time because we were getting pricked by these starfish. It's painful."