Dan Flynn watched from the pier as a hammerhead shark approached swimmers in Navarre, Fla.

He told ABC News '"I've seen sharks before but I've never seen a shark get that close. It was almost interacting with humans. From our vantage point, we could see the shark going towards a lady swimmer. And her back was to the shark, and she was unaware. You can hear people screaming in the video. I yelled, 'Get out of the water!'"

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