I understand how the ampullae of lorenzini works, but I think this thing is a joke.

Just because we know that the ampullae of lorenzini are sensitive to electrical energy or magnetic energy, doesn't mean in any way that having magnets around is going to make them not bite you. On top of that, these little magnets are surely not powerful enough to do anything.

The bottom line is that this is not a scientifically proven method to prevent shark attacks. The company knows this, but is praying on people because they know people are immensely afraid of sharks, even though the real danger is quite minuscule. The game is to sell these things to people that wouldn't have a problem with sharks anyway. They don't have a problem, so they believe the device is working. If the situation does arise where someone wearing the device does get bit, they just claim it doesn't work 100% of the time.

If someone buys this BS, they are wasting their money. I have the real shark repelling gear, if you want I can sell you what I have. It is guaranteed to work 99% of the time!!! It is a bag of special dog poop, you wipe it all over your gear before your dive. It will keep the sharks away and all of your dive buddies.