What type of currents appear and disappear suddenly?

Rip currents are fast swirls of water that can appear unexpectedly as they flow away from the shore. These currents are often found in areas with breaking waves, where the water that has been pushed toward the beach must return back to deeper waters. When waves break, they create a buildup of water along the shore, and the excess water can form a narrow channel that flows back out to sea. The sudden strength and presence of these currents can make them dangerous for swimmers and divers if they are not aware of them.

In contrast, stable currents and surface currents are generally more predictable and maintain consistent patterns over time. Undertow currents, while they do involve a return flow of water, typically occur below the surface and are not as immediate or sudden as rip currents. The defining characteristic of rip currents is their ability to emerge quickly and potentially catch individuals off guard, making them particularly notable for their suddenness.