A couple hours after sunset, everyone is donning a wetsuit. In minutes, 15 to 20 dark figures are standing in a graveyard on the west coast of Guam. But they're not here for the tombstones. They've come to help rescue something from dying in the waters nearby — the corals.
Corals along Guam's coastlines have been dying in recent years, and they're not alone. Warming seawater and increasing ocean acidity are damaging reef ecosystems around the world. Some scientists and environmentalists fear a worldwide collapse by 2050.