I watched a documentary in which a retired USN admiral, ...consistently said submarine-r. Since he had formerly been one, I leaped to the contusion that all USN submariners pronounced it the way their former boss did

He was talking for the benefit of civilians ... perhaps that explains it ... but must say I have heard both ... the subMARiner seems to be of more recent vintage.
Changing times?
Has your contusion interesting colors?
Aloha
wow