Cal. HNC § 655.2

(a) Every owner, operator, or person in command of any vessel propelled by machinery is guilty of an infraction who uses it, or permits it to be used, at a speed in excess of five miles per hour in any portion of the following areas not otherwise regulated by local rules and regulations:

(1) Within 100 feet of any person who is engaged in the act of bathing. A person engaged in the sport of water skiing shall not be considered as engaged in the act of bathing for the purposes of this section.

(2) Within 200 feet of any of the following:

(A) A beach frequented by bathers.

(B) A swimming float, diving platform, or lifeline.

(C) A way or landing float to which boats are made fast or that is being used for the embarkation or discharge of passengers.

(b) This section does not apply to the following:

(1) Vessels, including personal water craft, clearly identifiable as lifeguard rescue vessels engaged in public safety activities.

(2) Public safety vessels engaged in direct law enforcement activities or public safety activities that are displaying the distinctive blue lights prescribed by subdivision (a) of Section 652.5.

(3) Personal water craft, clearly identifiable as lifeguard rescue vessels or public safety vessels, operating within the surf zone.

(c) The vessels described in subdivision (b) are also exempt from any locally imposed speed regulation adopted pursuant to Section 660, but shall be operated in accordance with subdivision (c) of Section 655.7.

(d) For purposes of this section, the following terms have the following meanings:

(1) “Clearly identifiable as lifeguard rescue vessel” means an authorized lifeguard water rescue vessel operated by or owned by a public agency.

(2) “Public safety activities” include public agency sanctioned patrolling, traffic control, assisting disabled vessels, salvage operations, firefighting, providing medical assistance, search and rescue, and training.