I admit I was very skeptical on the Shark Shield when it first came out.
When I posted the video of the shark taking a fish from my hand in NZ,
http://youtu.be/EpbNMk7Y3ic , Shark Shield approached me and asked if I would be interested in their product.
They sent me a unit to test and I can tell you straight up it works. I have seen it first hand turn a shark away on a few occasions while shooting my show. I had a Tiger start swimming up to me in NC this year, I turned the unit on and the shark bolted. I have had the same situation with White Tips.
Will is dissuade a charging Whitey, I have no idea. But during those moments when you are in the landing process and have that fish struggling right next to the kayak it does work. This is the time I am generally the most concerned, not that the shark will hit me but that it will take my fish and in the process injure me or knock me from my kayak.
Is this something you need in LJ, you will have to make the call. In some of the very sharky places I have been, it sure gives a little added comfort. Particularly when you dangle your feet as much as I do.