A riptide is a strong, narrow current of water flowing away from shore toward the ocean. Despite the name, it's not actually a tide at all: it forms when waves push water onto the beach faster than it can flow back out. Eventually that water finds a gap, usually near a sandbar or pier, and rushes back to sea in a concentrated channel.

Riptides are dangerous because they can pull swimmers away from shore quickly. Trying to fight the current by swimming straight back toward the beach can exhaust even strong swimmers. Swimmers are often taught to escape a riptide by swimming parallel to the shore until they're out of the narrow current, then heading back to land.

Lifeguards watch for riptides constantly. You can sometimes spot them yourself by looking for areas where the water appears darker, smoother, or has a different color than the surrounding ocean.