It is unlawful for any person to operate any vessel in the harbor in such a manner as to jeopardize the same or to endanger life or property. When any power craft of less than 15 tons net burden is proceeding in such a manner that it is endangering any canoe, rowboat, skiff, or other watercraft, it is the duty of the person in charge of such power craft to reduce the speed, stop, or reverse as the case may be, to remove the danger to such watercraft or to refrain from willfully frightening the occupants thereof.