This role is critical when you stop for a swim, and most adults don't know to do it. Make sure the key is out of the ignition so nobody starts it while swimmers are in the water. We like the idea of hanging the key on a hook near the transom. That way, when the driver is ready to start the motor, he or she will be prompted to check the water for swimmers before firing up. Hanging the key near the walkthrough in the cockpit makes it easier to check the water behind the boat.
School one of the kids in radio language and proper channels so they'll understand how to communicate with authorities over the airwaves. The operator also helps you check to be sure the radio is operational before each excursion.