What sound is made when a vessel is signaling "distress"?

When a vessel signals a state of distress, it typically uses a sound signal consisting of a continuous blast or a series of repeated blasts on its whistle. This type of signaling is universally recognized as a call for immediate assistance on the water. Such a sound is distinct and urgent, intended to attract the attention of nearby vessels or shore facilities. It conveys the vessel's need for help and emphasizes the seriousness of the situation.

Other options, while they might serve various signaling purposes, are not used to indicate distress. A single short blast, for example, is often a signal for an intention to maneuver or communicate other operational messages. A bell ringing can be related to signaling mixes of intents but does not specifically denote distress. Similarly, playing a vessel horn in a melody does not conform to any recognized distress signal and is not effective in capturing urgent attention needed during emergency situations. Thus, the continuous or repeated blasts on the whistle stand out as the correct and recognized sound signal for distress.