Corals do not typically thrive in mangrove environments. However, corals are growing on and near the prop roots of red mangrove trees in Hurricane Hole, an area within the Virgin Islands Coral Reef National Monument under the protection of the US National Park Service in St. John, US Virgin Islands. This review summarizes current knowledge of the remarkable biodiversity of this area. Over 30 scleractinian coral species, about the same number as documented to date from nearby coral reefs, grow here. No other mangrove ecosystems in the Caribbean are known to have so many coral species. This area may be a refuge from changing climate, as these corals weathered the severe thermal stress and subsequent disease outbreak that caused major coral loss on the island’s coral reefs in 2005 and 2006. Shading by the red mangrove trees reduces the stress that leads to coral bleaching. Seawater temperatures in these mangroves are more variable than those on the reefs, and some studies have shown that this variability results in corals with a greater resistance to higher temperatures. The diversity of sponges and fish is also high, and a new genus of serpulid worm was recently described. Continuing research may lead to the discovery of more new species.