A Styrofoam cork with the top shaped to make it gurgle when yanked. The noise is supposed to imitate sounds of fish feeding on top, thereby attracting the attention of gamefish. The popping cork is very effective in saltwater, especially for sea trout. Most anglers will use a live or soft plastic shrimp with this setup, but you can use a variety of different baits if you choose.
It will work in freshwater as well, although, most freshwater anglers probably don’t even know what a popping cork looks like. Sunfish, white bass and largemouth bass can all be enticed for a closer look with the popping cork and a tasty minnow, nightcrawler or type of soft plastic may be perfect for drawing a strike.