California Code, Harbors and Navigation Code - HNC § 658.5

(a) Except as provided in subdivision (b), no person under 16 years of age shall operate a vessel powered by a motor of greater than 15 horsepower, except for a vessel that does not exceed 30 feet in length and is designed to use wind as its principal source of propulsion, or a dinghy used directly between a moored vessel and the shoreline or between a moored vessel and another moored vessel.

(b) Except as provided in subdivision (a), no person 12, 13, 14, or 15 years of age shall operate a vessel powered by a motor of greater than 15 horsepower, or a vessel that exceeds 30 feet in length and is designed to use wind as its principal source of propulsion, unless the person is accompanied in the vessel by a person who is at least 18 years of age and who is attentive and supervising the operation of the vessel.

(c) Subdivisions (a) and (b) do not apply to any of the following:

(d) Any person who violates this section, and any person who permits any other person under 16 years of age to operate a vessel in violation of this section, is guilty of an infraction.