What does a combination of two vertically disposed red lights and a lower white light indicate?

A combination of two vertically disposed red lights and a lower white light signifies that a vessel is not under command. This specific lighting configuration is established by the COLREGs as a way to communicate to other vessels that the ship is unable to maneuver as required by the rules. The two red lights indicate the vessel's inability to operate normally, while the white light serves as a means to increase visibility and alert other mariners of the vessel's status.

The misunderstanding may come from confusing these lights with those indicating other vessel statuses, such as fishing or being aground. However, the clear and defined signal of two red lights vertically stacked is specifically designated for vessels not under command, allowing for proper navigation and safety on the water.