Totally skier controlled what? A boat of course, duh!
This is the unmanned water skiing boat that’s controlled entirely by the skier. A six-button control panel on the tow rope handle sends signals to the boat, allowing skiers to start, accelerate, decelerate, turn, or stop the vessel with slight thumb movements. The nearly 8′-long boat has a three-cylinder, two-stroke 70 horsepower engine with jet pump and axial flow propulsion, generating speeds up to 40 MPH and creating wakes for jumps and other tricks. The jet propulsion engine is safer than propeller-powered crafts and provides superior acceleration and quicker planing–the time required to bring the skier and vessel level with the water surface.
More info: The Skier Controlled Tow Boat