Riptides are dangerous currents that drag people away from shore — but they also drag people back to shore:
Using GPS devices, he’s tracked them, and found that they circulate, coming back towards land. The accepted wisdom on what to do if you’re caught in a riptide is swim parallel to the shore to get away from the current, but professor Jamie MacMahan calculated that that gives you a good chance of being swept out to sea. Treading water for a three-and-a-half minutes yields a 90% chance of being brought back to shore.