Which distress signal can be used both day and night?

The use of flares is an effective distress signal that can be utilized both during the day and at night, making it a versatile option for mariners in emergency situations. Flares are designed to produce a bright light and are often accompanied by smoke or a loud bang, which enhances their visibility and audibility. At night, the bright light of a flare can be easily seen from great distances, alerting nearby vessels or search and rescue teams to the location of a distress situation. Even during daylight, when visibility may be more challenging, the vivid colors and brightness of flares still stand out against the natural backdrop, ensuring that they can draw attention effectively.

Other options like sound signals, visual flags, and smoke signals may have limitations based on environmental conditions or time of day, making flares a superior choice for continuous visibility in both circumstances.