Cal. Harb. & Nav. Code § 658.3

(a) A person shall not use a recreational vessel unless all of the following requirements are met:
1. (1) There is at least one wearable personal flotation device on board the vessel for each person on the vessel.
2. (2) Each personal flotation device is used in accordance with the requirements on its approval label.
3. (3) If a personal flotation device’s approval label refers to an owner’s manual, then the personal flotation device is used in accordance with the requirements in its owner’s manual.
(b) A person shall not use a recreational vessel 16 feet or more in length unless one throwable personal flotation device is onboard in addition to the number of wearable personal flotation devices required by subdivision (a).
(c) A person shall not operate a recreational vessel underway with a child under 13 years of age onboard unless at least one of the following requirements is met:
1. (1) The child is wearing an appropriate personal flotation device that is approved by the United States Coast Guard.
2. (2) The child is below deck or in an enclosed cabin.
(d) A person on board a personal watercraft or a person being towed behind a vessel on water skis, an aquaplane, or similar device, except for an underwater maneuvering device intended for use by a submerged swimmer, shall wear a United States Coast Guard-approved wearable personal flotation device that is used in accordance with approval labels and manufacturer’s instructions. An underwater maneuvering device is a towed or self-powered apparatus that a person can pilot through diving, turning, and surfacing maneuvers that is designed for underwater use.
1. (1) This subdivision does not apply to a person aboard a personal watercraft or a person being towed behind a vessel on water skis, if that person is a performer engaged in a professional exhibition, or preparing to participate or participating with authorization pursuant to a United States Coast Guard permit or other permit granted pursuant to subdivision (a) of Section 268 in an official regatta, marine parade, tournament, or exhibition.
2. (2) In lieu of wearing a United States Coast Guard-approved wearable personal flotation device as described in this subdivision, a person engaged in slalom skiing on a marked course or a person engaged in barefoot, jump, or trick waterskiing may elect to wear a wetsuit designed for the activity and labeled by the manufacturer as a water ski wetsuit. A United States Coast Guard-approved personal flotation device as described in this subdivision shall be carried in the tow vessel for each skier electing to wear a water ski wetsuit pursuant to this paragraph.
(e) The requirements set forth in subdivisions (a) and (d) do not apply to a person 13 years of age or older operating a recreational vessel if the vessel is engaged in an emergency rescue situation.
(f) Subdivision (a) does not apply to a person operating a “passenger vessel,” as defined in Section 2101(31) of Title 46 of the United States Code or a “small passenger vessel,” as defined in Section 2101(47) of Title 46 of the United States Code.
(g) For purposes of this section, the following definitions apply:
1. (1) “Enclosed cabin” means a space on board a vessel that is surrounded by bulkheads or canvas, and covered by a roof.
2. (2) “Underway” means all times except when the motorboat, sailboat, or vessel is anchored, moored, or aground.
(h) A violation of this section is an infraction punishable as provided in subdivision (a) of Section 668.