You have a better chance of winning the lottery than being killed by a shark in the United States. That's the kind of statistic people like to throw around when some coward friend mentions the possibility of encountering one of nature's most efficient killing machines while swimming in the ocean.
Well, guess what? People win the lottery all the goddamn time. I understand that it doesn't happen with the same frequency as car accidents or cloudy days, but it does happen. People win the lottery, and no matter how silly people want you to believe the idea is, people do get attacked by sharks. If the threat wasn't real, Googling the phrase "protect yourself from sharks" probably wouldn't return 875,000 results. If a shark attack was something you never needed to worry about, the movie Open Water wouldn't exist.
Even Jaws was based on some truly unfortunate s**t that really did happen.
The problem with this type of comparison is that it's usually taking the entire population into account. Figuring the landlocked citizens of Nebraska into shark attack numbers is absurd, as was pointed out by the Freakonomics people when that famous "vending machines cause more deaths than sharks" statistic made the rounds a few years back. There are so many factors that need to be considered before you can just toss that fact in your wallet and use it as universal shark protection.