Rip currents are powerful, channeled currents of water flowing away from shore. They typically extend from the shoreline, through the surf zone, and past the line of breaking waves. Rip currents can occur at any beach with breaking waves, including the Great Lakes.
Rip currents most typically form at low spots or breaks in sandbars and near structures such as groins, jetties, and piers. Rip currents can be very narrow or be hundreds of yards wide. The seaward pull of rip currents also varies: sometimes the rip current ends just beyond the line of breaking waves, but sometimes rip currents continue to push hundreds of yards offshore.
Rip currents form as incoming waves create an underwater sandbar close to shore (#1 above), and the waves push more and more water in between the sandbar and the shore (#2) until a section of this sandbar collapses and the water rushes back toward the sea (#3) through a narrow gap. Once the flowing water passes through the narrow gap, it begins to spread out (#4). It is here where the velocity and strength of the rip current circulation begins to weaken considerably.