Cal. Harb. & Nav. Code § 655
(j) Upon the trial of any criminal action, or preliminary proceeding in a criminal action, arising out of acts alleged to have been committed by any person who was operating a vessel or manipulating water skis, an aquaplane, or a similar device while under the influence of an alcoholic beverage in violation of subdivision (b) or (f), the amount of alcohol in the person’s blood at the time of the test, as shown by a chemical test of that person’s blood, breath, or urine, shall give rise to the following presumptions affecting the burden of proof: