In a situation with no other means of communication, how can a vessel signal for help?

A vessel can signal for help by sending up a series of flares because flares are recognized as visual distress signals in maritime regulations and are specifically designed to alert others to the presence of an emergency. When launched, they create bright, attention-grabbing signals that are visible from significant distances, especially at night or in poor visibility conditions. This method is a universally understood sign of distress, prompting other vessels or rescue services to respond to the situation.

While sounding a horn continuously might indicate alertness or the presence of another boat, it does not convey a specific message of distress per the established maritime communication protocols. Similarly, using radar does not function as a visual distress signal and cannot alert nearby vessels directly about an emergency in the same clear manner as flares. Displaying a registration number does not communicate any distress and serves merely to identify a vessel, lacking any urgency or indication of needing help. Thus, sending up a series of flares is the most effective and widely recognized method of signaling for assistance in emergency situations.