The term indicates a designated area on a body of water where vessels must operate at a speed that minimizes the waves, or wash, created by their movement. For example, a sign might indicate that boaters must proceed slowly and without creating a discernible disturbance to other watercraft or the shoreline.
Adherence to these zones protects fragile shorelines from erosion, safeguards smaller boats and swimmers from hazardous wave action, and preserves the tranquility of recreational areas. Historically, these regulations arose in response to increasing boating traffic and the associated negative impacts on waterways and surrounding communities.