Just my own experience.
Like OP's dad, I'm also a naturalized citizen, went on the 10 day (Mar 25 to Apr 4, 2022) sea of Cortez cruise, closed loop leaving from LA (San Pedro to be exact). My passport was going to expire on June 2, 2022. I didn't run into any problem with my passport. I have since renewed it, good for another 10 years.