What device is required when towing individuals on water skis?

When towing individuals on water skis, having a spotter is crucial for safety. The role of the spotter is to keep an eye on the skier at all times, ensuring their safety during the activity. The spotter's perspective from the boat provides necessary awareness of the skier's position, helping to identify any potential issues, such as falling, and allowing for timely reactions to prevent accidents.

While a life jacket is important for the skier’s personal safety and must be worn, it does not substitute for the extra visibility and communication provided by a spotter. Similarly, a whistle or flare gun may be useful for signaling in different contexts but are not specifically designed to assist in the active and ongoing monitoring of the skier while they are being towed. Thus, the presence of a spotter is a specific requirement aligned with ensuring a safer experience when skiing.