Cal. Harb. & Nav. Code § 651.1

As used in this chapter, unless the context clearly requires a different meaning, “bather” or “bathing” means a person floating, swimming, wading, or bodysurfing, with or without the use of a flotation device, including, but not limited to, floating upon or with the aid of a surfboard, paddle board, surfmat, innertube, life preserver, or air mattress, except a flotation device which is designed to be propelled by sail, mechanical means, power, oars, or paddle.