Sound production is known in more than 50, mostly stridulating, crustacean genera. These acoustic signals occur in agonistic interactions as well as for mate attraction. The mechanism of sound production in snapping shrimp, which also serves to stun or even kill small prey, is especially interesting. The current assumption was that the sound is produced by cocking and then rapidly closing the enlarged modified snapper claw. Snapping shrimp sounds contribute most to coastal biological noise, may be heard up to 1 mile away, and resemble the crackling of dry twigs in fire or the sizzle of frying fat. Recent hydrophone measurements close to tethered shrimp (Alpheus heterochaelis) revealed pulse-like signals of 500-ns duration, comprising frequencies beyond 200 kHz, and showing enormous sound pressure levels of up to 220-dB re 1 μPa (peak to peak) at 1-m distance. Such high intensities are very unlikely to be produced by the mechanical contact of two claw surfaces. Ultra-high-speed video recordings and simultaneous hydrophone measurements reveal that claw closure results in a water jet, the high velocity of which (25 m/s) leads to the formation of a cavitation bubble, which emits the extremely loud sound upon its collapse.