What must a vessel operator display whenever a skier is in the water?

A vessel operator must display a red or orange flag whenever a skier is in the water to signify that a person is engaged in water sports. This flag serves as a warning to other boat operators and nearby water users to exercise caution in the area, as there is a potential hazard due to the presence of a skier who may fall or need assistance.

The use of a red or orange flag is a standard safety practice that enhances visibility and helps ensure everyone on the water maintains awareness of the skier's location. The flag's color is significant, as these bright colors stand out against the water and surroundings, making it more noticeable for navigation safety.

Other colors, like yellow or white flags, do not convey the same level of urgency or specific meaning regarding water skiing activities, which is why they are not the correct options. Understanding the importance of these signaling practices is crucial for promoting safety on the water.