Bleaching of coral is like sunburn to human skin. There are different levels of bleaching damage. Half of the Great Barrier Reef has been bleached to death since 2016. Mass coral bleaching, a global problem triggered by climate change, occurs when unnaturally hot ocean water destroys a reef’s colorful algae, leaving the coral to starve. The Great Barrier Reef illustrates how extensive the damage can be: Thirty percent of the coral perished in 2016, another 20 percent in 2017. The effect is akin to a forest after a devastating fire. Much of the marine ecosystem along the reef’s north coast has become barren and skeletal with little hope of recovery. The Reef and Rainforest Research Centre (RRRC) in cooperation with the Association of Marine Park Tourism Operators (AMPTO) conducted detailed surveys of bleaching levels at key dive tourism sites around Cairns in 2016. While many of the primary dive sites were not affected in the 2016 bleaching, quite a few were quite strongly affected in the 2017 event. Fortunately, these are the same reefs showing strong signs of recovery. Coral bleaching occurs when corals experience too much stress – i.e. from high water temperatures or poor water quality – and eject their symbiotic zooxanthellae, losing their distinctive colors. If stressful conditions persist, the corals will die, but if conditions return to acceptable levels, some corals can re-absorb zooxanthellae and recover.