A buoy marked with a red light may indicate which of the following?

The statement that a buoy marked with a red light may indicate an isolated danger is accurate. In the U.S. Aids to Navigation System, red lights are typically associated with isolated danger marks. These buoys are used to indicate a specific hazard, such as a submerged rock or wreck, that poses a risk to navigation and is surrounded by navigable water.

The primary function of an isolated danger mark is to signal to mariners that while the area around the danger is safe to navigate, the buoy itself represents an obstruction that must be avoided. The presence of a red light reinforces this warning, making it visually identifiable even in low visibility conditions.

In contrast, a safe-water mark typically displays a single light, can be red or green, and indicates that it is safe to pass on either side. Marks indicating the right side of a channel are designated with green colors and are numbered accordingly. Daymarks refer to the visual characteristics of a buoy used during daylight and do not pertain to specific lights or the indication of dangers.