Cal. Health & Safety Code § 18075.55

(a) Floating homes subject to real property taxation pursuant to Section 229 of the Revenue and Taxation Code shall be subject to registration and titling by the department only at the time of sale, resale, or transfer of title.
(b) Ownership registration and title to a floating home may be held by two or more co-owners in the manner specified in Sections 18080 and 18081.
(c) Upon receipt of a registration card, every registered owner shall maintain the card or a copy thereof with the floating home for which it is issued.
(d) “Floating home,” as used in this section, means a floating structure which is all of the following:
1. (1) It is designed and built to be used, or is modified to be used, as a stationary waterborne residential dwelling.
2. (2) It has no mode of power of its own.
3. (3) It is dependent for utilities upon a continuous utility linkage to a source originating on shore.
4. (4) It has a permanent continuous hookup to a shoreside sewage system.
  This section does not affect existing law regarding residential use of tide and submerged lands.