California Code, Revenue and Taxation Code - RTC § 227

(a) In the taking and possession of fish or other living resource of the sea for commercial purposes.

(b) In instruction or research studies as an oceanographic research vessel.

(c) In carrying or transporting seven or more people for hire for commercial passenger fishing purposes and holds a current certificate of inspection issued by the United States Coast Guard. A vessel shall not be deemed to be engaged or employed in activities other than the carrying or transporting of seven or more persons for hire for commercial passenger fishing purposes by reason of that vessel being used occasionally for dive, tour, or whale watching purposes. For purposes of this subdivision, “occasionally” means 15 percent or less of the total operating time logged for the immediately preceding assessment year.