What position must a vessel transmit during a distress call?

When a vessel transmits a distress call, it is crucial to provide its position for effective search and rescue operations. The standard practice is to communicate the vessel's position in latitude and longitude format. This format is universally recognized and allows rescuers to accurately determine the vessel's location on the globe, facilitating swift assistance.

Using latitude and longitude provides precise coordinates that define a point on the Earth’s surface, making it the most effective way to convey location information in emergency situations. The clarity and universality of these coordinates ensure that response teams can find the vessel quickly, regardless of the region or navigational standards in use.

In contrast, other options such as expressing the position in cubic meters or providing the nearest port location do not yield the same level of accuracy needed for effective rescue. Additionally, transmitting the last known speed does not indicate the location of the vessel, which is the primary concern during a distress call. Therefore, conveying a vessel's position using latitude and longitude is the essential information needed during emergencies at sea.