As global average temperatures rise, many coral reefs are experiencing a phenomenon called "bleaching", leaving behind brittle structures which often stand very little chance of recovery. Coral reefs, sometimes called "the rainforests of the ocean", are highly sensitive underwater ecosystems. So how many of them can still be saved? Trevor and Joey look into how corals grow, how we study them, and the symbiotic relationships living all over their reefs, with expert commentary from coral reef recovery researcher Aziz Mulla.