Rip currents are dangerous primarily because they are often more powerful than they initially seem and move quickly, which can catch even experienced swimmers off guard and pull them away from shore. Such currents, which occur in a direction approximately perpendicular to the shoreline, are narrow, jet-like streams of water which typically reach velocities of up to 1 meter per second (about 3.3 feet per second), or 2 knots. However, some rip currents have reached speeds of up to 2.4 meters per second (8 feet per second), or about 5 knots. Rip currents can be difficult to spot, leading many swimmers to panic and struggle when encountering them.

Rip currents typically occur at long coastlines where wave trains approach parallel to shore. The buildup of water from incoming waves eventually finds a release point, or a path of least resistance, surging seaward through a low point or gap in a breaker. This sudden formation can catch swimmers by surprise, increasing their risk of being swept away.

Rip currents can be misleading at first sight because they often appear as calm patches of water between breaking waves. Swimmers may mistakenly enter such areas, believing they are safer, only to find themselves caught in a strong current. The water in rip currents may be discolored by suspended sand, but this is not always noticeable from the shore, making them all the more dangerous. It is recommended to swim parallel to the shoreline to escape the current rather than attempting to swim against the flow of water.