It shall be the duty of every operator of a vessel involved in a collision to stop and render assistance as required by § 29.1-739. If any person knowingly fails to comply with the provisions of § 29.1-739 when the collision, accident or other casualty results in serious bodily injury to, or the death of, any person, he shall be guilty of a Class 6 felony. If any person knowingly fails to comply with the provisions of § 29.1-739, when the collision, accident or other casualty results only in damage to property, he shall be guilty of a Class 1 misdemeanor. However, if the vessel struck is unattended and the damage is less than fifty dollars, such person shall be punished only by a fine not exceeding fifty dollars.