The word bikini evokes beaches and a cartoon sponge, but it belongs first to Pikinni, meaning surface of coconuts, a Marshall Islands atoll whose 167 residents were asked in February 1946 to leave for the good of mankind. Between 1946 and 1958 the United States detonated 23 nuclear devices there, including the 15-megaton Castle Bravo shot that vaporized three islands and left a mile-wide crater.

This episode follows the Bikinians from their matrilineal land culture and asymmetrical proa canoes through exile on Rongerik, Kwajalein, and Kili, a 1972 return poisoned by cesium-137 in coconuts, and the recent depletion of a $59 million trust fund. It closes with the atoll's strange present: thriving reef sharks, a sunken ghost fleet including USS Saratoga, restricted dive tourism, UNESCO status, SpongeBob mutation theories, and a swimsuit named  ...