Final answer:
A small vessel like a dingey, which lacks fixed navigation lights, is required to show a white light from a lantern to prevent collisions according to maritime regulations. The white light serves as an all-round light and must be shown in sufficient time to allow other vessels to avoid a collision.
Step-by-step explanation:
The question is related to maritime navigation and the use of lights to prevent collisions at sea. According to international maritime regulations, boats and ships are required to display lights at night so that other vessels can see them and determine their size, type, and direction of travel to avoid collisions. The specific vessel that would need to show a white light from a lantern, in this case, would be a small vessel, such as the dingey mentioned in the narrative, that does not have fixed navigation lights. It must display a white light in time to prevent a collision if it encounters other vessels.
The white light serves as an all-round light visible for 360 degrees and can be seen from a sufficient distance to give other vessels time to take measures to avoid a collision. The lantern should be shown in time, which means as soon as the operator of the small vessel determines there is a risk of a close encounter with another vessel. The international regulations for preventing collisions at sea, known as COLREGs (International Regulations for Preventing Collisions at Sea), specify the lighting requirements for vessels of different sizes and types. For instance, larger vessels have a combination of white, red, and green lights that allow other vessels to ascertain their heading and actions they are likely to take.