Sonic is a 12 volt 360 degree sounding device that attracts big sharks.  This is a must have unit that will save you time and money on gas.  Sonic is a proven fish attracting device that should be used anytime you’re chumming for sharks.
As you know, shark fishing isn’t cheap. You have invested an untold amount on your boat and in equipment, rods, reels, and gaffs. After spending all this money, you probably think you’re all set and ready to go, but if you’re really serious about catching the beasts and winning tournaments, there’s one thing left to get: an electronic attractant. Though the device itself is fairly expensive, it pays for itself very quickly. When you consider how much you spend on gas and chum, you don’t want to come home empty-handed. This device attracts Mako sharks. Each time I use an electronic attractant, more fish are attracted to the boat. When I don’t use this device, I often see monster sharks swim through the slick and leave. They will eat the bait that was eating your chum 50 yards behind the boat, without approaching your boat.
The Sonic
The Sonic imitates the sound frequencies that a wounded bait fish would produce, which attracts sharks. The Sonic gives off this low frequency tone of acoustic vibrations in a 360 degree pattern, inviting sharks to the boat. The Sonic can be heard for at least one mile through the water. While chum is only spread in one direction, this device rings the dinner bell in all directions.
Typically a shark approaches the boat because the chum slick has attracted it. Most of the time it doesn’t head straight for the chum bucket. Sharks have bio-electrical sensors called ampullae of Lorenzini, (see The Mako Shark) which help sharks find low frequency electrical currents emitted by fish. Because of the many electrical currents generated by your boat, (the grounding system tied in with the motor and zincs) the shark usually heads for the propeller, which protrudes from the boat giving off an electrical current. (This is why some sharks bite into the propeller). The next thing sharks tend to investigate is the chum bucket. The Sonic is such a strong attractant that sharks will bypass the propeller, the zincs, and the chum bucket to head straight for the Sonic.