Final answer:
Red sectors of navigation lights warn mariners of shoals or nearby land, marking hazardous areas to avoid in order to prevent running aground.
Step-by-step explanation:
Red sectors of navigation lights are used as a navigational aid to warn mariners of shoals or nearby land. These lights help in indicating hazardous areas where ships should not navigate to avoid running aground or colliding with landmasses. In nautical terms, a shoal is a natural submerged ridge or bank, often made up of sand or rocks, which poses a hazard to navigation due to its shallow waters.
Lighthouses, as mentioned in the provided references, serve a vital role in maritime navigation by emitting light beams to guide ships at sea. A lighthouse in California, for example, rotates its light to cover all directions, making sure ships are warned not to approach the dangerous shoreline too closely. Therefore, the function of red navigation lights is crucial in keeping seafarers safe by marking areas to avoid, thereby assisting in the safe passage of vessels.