What size must the skier down flag be at minimum?

The correct answer is based on the regulations regarding ski down flags as they pertain to visibility and safety. A down flag must be a minimum size of 12 inches by 12 inches to ensure it is easily visible to other boaters and participants on the water. The size is designed to allow other individuals to recognize the signal quickly, which is crucial for maintaining safety while someone is skiing. A flag of this dimensions can stand out effectively, alerting other boaters to be cautious and maintain a safe distance.

Larger flag sizes, while they may improve visibility even further, are not required by the regulations, making the 12-inch by 12-inch size the minimum size that meets legal requirements. Additionally, smaller options, like a 6-inch by 6-inch flag, would not provide the necessary visibility to alert others, potentially leading to dangerous situations on the water. Hence, the minimum size regulation helps establish a standard for safety during water sports activities like skiing.