From the California Boater Card FAQ:
Q: Who will be exempt from needing a Boater Card?
A: According to California law the following persons will not be required to have a boater card to operate a motorized recreational vessel on California waterways when the requirements go into effect beginning in January 2018:
• A person operating a rental vessel.
...
• A person who is a resident of a state other than California who is temporarily operating a vessel in California for less than 60 days and meets the boating requirements, if any, of his/her state.
• A person who is a resident of a country other than the United States who is temporarily operating a vessel in California for less than 90 days and meets the boating requirements, if any, of his/her country.
And so on....
California Boater Card FAQ
Q: Who will be exempt from needing a Boater Card?
A: According to California law the following persons will not be required to have a boater card to operate a motorized recreational vessel on California waterways when the requirements go into effect beginning in January 2018:
• A person operating a rental vessel.
...
• A person who is a resident of a state other than California who is temporarily operating a vessel in California for less than 60 days and meets the boating requirements, if any, of his/her state.
• A person who is a resident of a country other than the United States who is temporarily operating a vessel in California for less than 90 days and meets the boating requirements, if any, of his/her country.
And so on....
California Boater Card FAQ