Which shape might indicate a "no wake" zone?

A circle is commonly used to indicate a "no wake" zone in boating. This shape effectively communicates that vessels should reduce their speed to avoid creating wakes that can cause potential hazards to others on the water, such as erosion of shorelines or disturbance to other watercraft and their passengers. The circular shape is easily recognizable and is traditionally associated with regulatory signs, making it an effective choice for notifying boaters to adhere to specific speed restrictions.

While other shapes like squares, triangles, and diamonds may be used for various other navigational markers or warning signs on the water, they do not typically denote a "no wake" zone. The circle's established association with speed restrictions helps ensure that boaters can quickly and accurately interpret the message while navigating.