It shall be unlawful for any person under the age of 16 to operate any vessel powered by a motor or motors generating a total horsepower in excess of 10 horsepower; except, it shall be lawful for a person under the age of 16 to operate a vessel powered by a motor or motors generating a total horsepower of more than 10 horsepower as long as they are under the direct supervision of a parent or legal guardian in the vessel.