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My first thoughts actually were, that it was build to detect (and maybe drive off) sharks.

And dolphins and co. are sensitive to sonar and you would likely drive them away. Sharks not so much. But I lack detail knowledge.

Sharks are sensitive to electrical signals, so it would be interesting to see if we could generate ones they don't like.

There are lots of shark repellent products already on the market, some of them electric:

And some of them magnetic, similar to those anti-nausea magnet bands. Some of them work, some don't.

Just waiting for someone with a magnet on their ankle to get it bitten off and sue the manufacturer...