California Code, Harbors and Navigation Code - HNC § 501

(a) “Department” means the Department of Motor Vehicles or any successor agency thereto which registers vehicles.

(b) “Mail” means first-class mail, postage prepaid, unless registered mail is specified.  Registered mail includes certified mail.

(c) “Services” means the making of repairs or performing labor upon or to, and the furnishing of supplies or materials for, any vessel or any trailer used in connection with a vessel.

(d) “Storage” means the safekeeping, mooring, berthage, wharfage, or anchorage of a vessel and the providing of parking space for any trailer used in connection with the vessel.

(e) “Vessel” means every description of watercraft, other than a seaplane on the water or a floating home, used or capable of being used as a means of transportation on the water and required to be registered, excluding any vessel which has a valid marine document issued by the United States or any agency thereof.  For the purposes of this article, “vessel” includes any trailer used in connection with the vessel which is in the possession of the lienholder at the time the lien arises.