What is the term for an area of smooth water found between two upstream points, often seen in river settings?

The term that best fits the description of an area of smooth water found between two upstream points in a river setting is "pool." In river terminology, a pool is typically characterized by deeper, slower-moving water, providing a contrast to more turbulent sections such as rapids.

Pools are formed in various ways, including the natural topography of the riverbed or as a result of water flow dynamics that cause sediment to settle, creating a refuge for fish and other aquatic life. This calm water is essential for various ecological processes and is often used by river rescuers to identify safe zones for entry or recovery operations.

Other terms listed, like "water hole," "tongue or chute," and "cascade," refer to different river features. A water hole often describes a specific deep area within a pool but is not used interchangeably with the term pool itself. A tongue or chute refers to a narrow, fast-moving section of water leading into calmer areas but does not represent smooth water. Similarly, a cascade denotes a waterfall-like effect where water flows over rocks, which is contrary to the smooth water characteristics needed in this context. Understanding these terms helps in better navigation and assessment of river environments for safe rescue operations.