Hi, my question to you is: Should the words admiral and captain in the following sentence be uppercase or lowercase? (My feeling is lowercase, as there are no names attached.)

"The captain turned toward the sonar operator and instructed him to quickly relay the nearest submarine's coordinates."

And secondly, would the word 'captain' be a proper noun??
Thank you in advance for your help!

lowercase.

Why do you think 'captain' would/could be a proper noun?

Short answer: I don't think that it should. I asked that question just in case the person writing the book insisted on it.

Thank you very much!