Shark Repelling Device Sales Increase After Three Attacks

Sales of an Australian-made device to repel sharks are booming after three recent attacks in Sydney. SeaChange Technology, the company that produces the Shark Shield, says inquiries have tripled over the past two months and sales have increased by 50 per cent.
The company can barely keep up with production.
The device, which costs between $600 and $700 depending on the model, weighs less than 3 ounces and can fit into the palm of a your hand. It works by releasing electrical impulses that are painful to sharks within about 25 ft of the device.
I’ll take two.
[source]




Just curious, what are they made of and how do they stay waterproof?
what other fish does it effect? sonar tests done by the navy have been bad for whales and dolphins(or any other creature that uses sonar to communicate or navigate) so if it is painful to sharks, what does it do to other fish?