“Beach, eat, drink, dance, repeat.” These are Rihanna’s favorite things to do in Barbados. In a June 7 interview with Conde Nast Traveller, the pop star gushed over her home country, a small island nation in the middle of the Caribbean. “When I’m in Barbados, all is right with the world,” she said. But not all was right with Barbados.

The same day, the local The Daily Nation newspaper reported on an “invasion of the Sargassum seaweed”—a brown, leafy algae that had washed up in thick mats on the white-sand beaches of the island’s eastern shores. The next day, the country’s government declared it a national emergency. Seen from afar, the bloom looked like a coppery oil spill slicking the sea. But a closer look revealed dead wildlife entangled within it.

The June Sargassum invasion in Barbados claimed the lives of three sea turtles, six dolphins, and “countless” fish and eels, The Daily Nation reported. But surely more have perished in the months since, as sheets of the bulbous-tipped seaweed—sometimes several feet deep—have become regular visitors to the country’s eastern and southern shorelines.

A dead baby sea turtle in beached Sargassum seaweed in Palm Beach, Florida. Nancy Jones Peterson

“We’ve had mass mortality of sea turtles that have gotten trapped under ever-thickening piles,” said Hazel Oxenford, a Barbados-based fisheries biologist at the University of the West Indies. “When the turtles try to come up for air, they drown.” Because these Sargassum beachings are primarily happening during nesting season, which runs from March until the end of October, baby turtles attempting to crawl from their eggs toward the ocean are also getting caught in it.

Barbados isn’t alone. In the last six months, more than 700 beaches across the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico have been hit with mass beachings. Mexico, Belize, Guadeloupe, Martinique, and the British Virgin Islands are covered in it, taking a toll on tourism and fishermen alike. “The fishermen could not go to sea for two or three days,” a worker in Dominica told Hakai Magazine. “They couldn’t get the boats out because it was so thick.” South Florida, too, has seen an “assault.” It’s the worst year for Sargassum beachings ever.