Safety
Spotter / observer
A dedicated second person besides the driver whose only job is to watch the rider and relay their status, legally required in most jurisdictions for towed watersports.
A spotter (also called an observer) is a person other than the driver whose sole responsibility is to keep eyes on the rider at all times and communicate with the driver, including signaling when the rider falls. Most U.S. states legally require a spotter for any towed watersport; many specify a minimum age (often 12, sometimes as low as 10 or higher depending on the state). Some states allow a wide-angle mirror as a substitute, but a human spotter is the safer and often mandatory standard.
The spotter's job is critical because a downed rider in the water near the boat is easily lost from the driver's view, and a prompt fallen-rider signal lets the driver cut power and circle back safely.