The first dorsal spine is modified into an illicium, a movable rod tipped with an esca, a fleshy lure. In the striated frogfish the esca is a bunch of filaments that the fish waves in a manner resembling a polychaete worm. Prey approaches to inspect it.
The strike itself is one of the fastest feeding movements measured in vertebrates. The mouth opens explosively, the buccal cavity expands to around twelve times its resting volume, and water plus prey rushes in. Published timings for frogfish strikes are in the range of about six milliseconds, well below the reaction time of the small fish and crustaceans they take. The mouth then closes and a valve prevents the prey escaping with the expelled water.
Everything else about the fish is slow. It does not chase, it walks on jointed-looking pectoral and pelvic fins, and it can remain effectively motionless for long periods while its skin texture and colour match sponge or algal cover. Colour change happens over days to weeks, not instantly, which distinguishes it from the fast chromatic shifts of cephalopods.