In any county of this State in which there exists any harbor, bay, inlet, or other arm of the sea, the board of supervisors, upon receiving a petition signed by persons who are both freeholders and electors in such county, equal in number to at least fifteen per cent of the vote cast in the county for the office of Governor at the last preceding election, asking that the matter of issuing bonds of the county for the purpose of improving, developing or protecting the harbor, naming it by the name by which it is commonly called, be submitted to the electors of the county, may appoint a harbor commission for the county, which shall perform the duties and exercise the powers specified in this chapter.