How can a vessel visually signal distress if it becomes disabled?

The correct method for a vessel to visually signal distress when it becomes disabled is by displaying a bright orange flag with a square and ball. This signal is recognized internationally as a clear indication of distress. The orange flag with a square and ball is part of the standard maritime signals specified by the International Convention for the Safety of Life at Sea (SOLAS), and it is designed to get the attention of other vessels or authorities in the vicinity.

The other choices do not effectively communicate a distress situation in accordance with established maritime protocols. While red and white banners or firing a gun at intervals may suggest alertness or warning, they are not universally recognized as distress signals. Sending series of light signals can be useful in certain situations, but it also lacks the direct recognition that the orange flag provides. Thus, the bright orange flag with a square and ball remains the most effective and universally understood means of visually signaling distress while at sea.