Cal. Harbors and Navigation Code § 681

(a) It is unlawful to operate a motorized vessel or have the engine of a motorized vessel run idle while an individual is teak surfing, platform dragging, or bodysurfing behind the motorized vessel. (b) It is unlawful to operate a motorized vessel or have the engine of a motorized vessel run idle while an individual is occupying or holding onto the swim platform, swim deck, swim step, or swim ladder of the vessel. (c) Subdivision (b) does not apply when an individual is occupying the swim platform, swim deck, swim step, or swim ladder for a very brief period of time while assisting with the docking or departure of the vessel, while exiting or entering the vessel, or while the vessel is engaged in law enforcement or emergency rescue activity. (d) “Teak surfing” or “platform dragging” means holding onto the swim platform, swim deck, swim step, swim ladder, or any portion of the exterior of the transom of a motorized vessel for any amount of time while the motorized vessel is underway at any speed. (e) “Bodysurfing” means swimming or floating on one’s stomach or on one’s back on or in the wake directly behind a motorized vessel that is underway. (f) “Vessel” has the same meaning as set forth in subdivision (e) of Section 775.5. (g) A violation of this section is an infraction punishable by a fine of up to one hundred dollars ($100). Nothing in this subdivision shall be considered in relation to a suspension, restriction, or delay of driving privileges, or in the determination of a violation point count as provided in Section 12810 of the Vehicle Code.