Final answer:
Boats are often required to keep out of areas marked by navigational aids that denote danger such as dams, waterfalls, and rapids. These areas, like The Falls of the Ohio in Louisville, signify a break of bulk point dubbed a head of navigation where boats must stop. Dams can significantly alter local ecosystems and pose navigational barriers.
Step-by-step explanation:
The symbol that often represents areas where boats should keep out, such as dams, swim areas, or rapids, can vary depending on the local regulations and signage. However, universally, such areas may be marked with navigational aids like buoys, signs, or flags that denote danger and signal boaters to avoid these hazardous locations. Areas like waterfalls also pose a significant barrier to navigation. The presence of a waterfall, as in the case of The Falls of the Ohio by Louisville, Kentucky, requires boats to stop due to the water tumbling over, creating a break of bulk point called a head of navigation. Similarly, dams like the one over Carrying Place Inlet or the large dams affecting biodiversity, as in the case of the Siberian Cranes and the Yangtze River Dolphin, represent significant obstacles that necessitate detours and have wider environmental impacts. Moreover, certain coastlines may also imply no-go areas for boats due to natural protection against waves or conservation efforts.