What must WIG craft exhibit when not in flight?

When a WIG (Wing-In-Ground) craft is not in flight, it is not required to exhibit any additional lights beyond what would typically be necessary for its operational state. WIG craft operate close to the surface of the water and when they are on the ground or at rest, they do not need to display navigational lights. Essentially, this reflects the fact that the craft is not in a position where it poses a navigational hazard, and therefore does not require the same lighting as powered or sailing vessels that are underway.

The other options imply that certain lights must be displayed, which does not apply when the craft is on the ground. For instance, an all-round white light would be used for visibility when the craft is operational at sea, but its non-flight status means that is unnecessary. Similarly, high-intensity all-round red lights are typically used to indicate danger or a particular hazard, which is not applicable when the craft is stationary. Lastly, a masthead light is designated for vessels underway, and therefore also does not apply when the WIG craft is not in flight. Understanding the specific requirements for WIG craft during different operating states is crucial for safe navigation and compliance with COLREGs regulations.