The previously posted CA boating regulation was for powerboats. The appropriate section for most beach cats is:

Visual Distress Signals (Coastal Waters Only): Boats less than 16 feet,
manually propelled craft of any size, sailboats under 26 feet — of completely
open construction and not equipped with propulsion machinery, and boats
competing in an organized marine parade, regatta, race, or similar event are
only required between sunset and sunrise to carry aboard devices that are
suitable for night use (see page 43).