If you've ever witnessed a great white shark attack, you know the meaning of the word "relentless." The giant creature's dorsal fin traces a circle in the water as it spots a vulnerable victim; the shark makes a first strike, then a second and a third, coolly and methodically; the victim struggles, weakens and finally succumbs to the massive loss of blood. Some victims survive, of course --- but for many, once marked for attack, it's only a matter of time.

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