Recent research shows that fish are attracted to healthy reef systems through sound. In their efforts to rebuild coral reefs, marine biologists played audio recordings made in 2017 before cyclones and bleaching events devastated the Great Barrier Reef. To their astonishment, two times as many fish returned to the area. "Fish whistle and grunt, sea urchins scrape food from the seabed, dolphins squeal," Hakai writes in his paper. Friendly sounds remind fish that home is where the noise is.