Safety
Observer law
State and local regulations requiring a qualified observer (spotter) aboard, in addition to the driver, whenever a rider is being towed.
Observer laws are the legal rules mandating a spotter for towed watersports. The exact requirement varies by jurisdiction: many states require an observer of a minimum age (for example, California requires an observer at least 12 years old), and some allow a wide-angle rear-view mirror in place of, or in addition to, a human observer. The observer must continuously watch the rider and communicate with the driver.
Riders and drivers are responsible for knowing the rules of the specific lake or state they're on, since age thresholds, mirror allowances, and other details differ widely.