Director Greg MacGillivray, a documentary filmmaker whose specialty is the natural world, turns his camera on the South Pacific's beautiful but potentially endangered coral reefs. Backed by narration from Liam Neeson and music by Crosby, Stills and Nash, MacGillivray's film focuses on the the underwater work of a husband-and-wife duo. As they survey the waters near Australia, Tahiti and Fiji, Howard and Michele Hall explain what must be done to preserve the reefs.