A plunge pool is a feature of waterfalls. When a river falls from a height, the water hits the pool below with great force, causing erosion. Over time, the pool gets deeper, and the rocks at the bottom get smoother. Plunge pools can be dangerous to swim in due to the strong currents and swirling water at the base of the waterfall. However, they can also be beautiful and attract tourists. Many waterfalls are popular tourist attractions because of their plunge pools, which visitors can swim in under the right conditions.