What is required for legally towing a water skier?

To legally tow a water skier, having an observer or a mirror for visibility is essential. This requirement is in place to ensure that the operator of the boat can safely monitor the skier at all times. An observer acts as an extra pair of eyes, alerting the operator to any issues that may arise, such as the skier falling or needing assistance. The use of a rearview mirror can also provide the operator with a better vantage point to ensure the skier's safety without needing to constantly turn around.

While the other options may seem relevant, they do not fulfill the legal requirements for towing water skiers. For example, a second boat is not necessary for this activity; one boat can effectively perform the task with the proper observation measures in place. Similarly, a license for the water skier is not a standard requirement in most jurisdictions; it is the boat operator who needs to have the appropriate credentials. Lastly, a spotter on land is not relevant in this context, as the observer or mirror must be on the boat to ensure on-the-water safety during the activity.