Do Shark Repellants Work?

"So, do these repellants work? Hard to say, since testing them out is so difficult. For one thing, there's a distinction between deterring curious sharks and preventing an ambush-style attack by a 2,000-pound great white traveling at 20 knots. It's easier to create a test situation that replicates the former than the latter. But, even then, it's extremely costly and time-consuming—you have to rent a tank, bring in sharks, and prove that they're physically repelled by the substance and not just bored."

When Sharks Don't Attack
by Christopher Beam
http://www.slate.com/id/2211069/