Editing Whitewater (section)

=== Strainers or sifts ===
Strainers are formed when an object blocks the passage of larger objects, but allows the flow of water to continue – like a big food [[strainer]] or [[colander]].  These objects can be very dangerous, because the force of the water will pin an object or body against the strainer and then pile up, pushing it down under water. For a person caught in this position, getting to safety will be difficult or impossible, often leading to a fatal outcome.

Strainers are formed by many natural or man-made objects, such as storm grates over tunnels, trees that have fallen into a river ("log jam"), bushes by the side of the river that are flooded during high water, wire fence, rebar from broken concrete structures in the water, or other debris. Strainers occur naturally most often on the outside curves of rivers where the current undermines the shore, exposing the roots of trees and causing them to fall into the river and form strainers.

In an emergency, climbing on top of a strainer may be better so as not to be pinned against the object under the water. In a river, swimming aggressively away from the strainer and into the main channel is recommended. If avoiding the strainer is not possible, one should swim hard towards it and try to get as much of one's body up and over it as possible.