A Massachusetts family cut its time on a Cape Cod beach short after they were warned of a great white shark in the area.
But it wasn't a lifeguard who notified the beachgoers — it was the Atlantic White Shark Conservancy's "Sharktivity" app.
"I clicked on the app, and looked at the map, and it said the sighting was 20 minutes ago, so I thought, 'We should be careful,'" Beth Kressley Goldstein told the Boston Globe. "My youngest [child] was on the edge of the water, and I said, 'Annie, don't go swimming today.'"
Members of Goldstein's family had already boarded their boat, steps from the Chatham shore, but she was standing on the shore when she noticed the shark.
"My daughter took a picture of it. It was right off the boat," she told the Globe. "We were kind of thrilled — it's such a cool thing to be able to see. But I was a little bit nervous."