who confesses he's never cooked jellyfish before. He's going to fry it in a tempura batter made of potato, wheat and rice flours, mixed with sparkling water. "No salt?" I ask. "Zero," he tells me.

Jellyfish are known for drifting to and fro at the whim of ocean currents—but not all species are so passive. The millions of golden jellyfish that pack Palau’s Jellyfish Lake spend much of ...