I know you already wrote that you found the answer you were looking for. But I'm going to throw my 2 cents in here anyway.
I kind of like how some actually mention gender... cause I def think that if you were a 26 yr guy and he was a 18 (soon to be 19) yr. girl... no one would use the word creepy! Than again I study gender and gender related topics and this social conception of things (How something's are OK for a guy, but not for a gal... )
Personally I don't find it creepy! At least no more creepy than a 26 year old guy dating an 18 year old female. I am the same age as you however, I'm 26 almost 27 (wooot woot) and I would personally never date someone who is 18. But of course that's me... haha I won't even date someone who is younger than 24... (which says more about me than anything else I think)
I actually talked to a friend about this the other day after reading a blog about someone who is 18 (female) who has a boyfriend who is 43... and I think that if I brought home a guy to my parents house who was under the age of 20... and one who was still in high school they would def have a talk to me about it and ask me what I was doing...
I also am the kind of person who would think of it as inapropriate for a guy our age to date someone under the age of 20... so yeah...
And yes, the navy situation also brings up some questions I guess. As well as how long have you know each other etc.
And yes, you did ask about dating and not marrige, and I took that into consideration as I was writing this.
Hope this came of as helpful and not judgmental
Best of luck though!