Not just the Marines, but most young men in or out of the military. There's a reason why Playboy and other like magazines have been in business for so long, and it ain't the fascinating articles and interviews.
'cept, of course, Playboy and like magazines aren't sold on military bases.
Even if they aren't sold in the PX, they will still get dirty pictures to look at.
Ever been to Italy or France? If you ever go, check out some of the magazines they are selling in the newstands there. Some of them make Hustler look like Hi Lites.
And then, there is the fact that there are VCRs and DVD players all over the ship, many people have their own personal one, and with that, some of them even have a porn stash. There was a dude in my squadron named Johnny who was the squadron porn king. He had a cruise box full of dirty tapes. And, for those of you who don't know how big a cruise box is, they are about 3 ft, by 2 ft, by 2 ft. He even had a copy of the chick that was a sportscaster who made a dirty movie with her boyfriend where she was fisted.
Nope, sorry, but the sex drive is too strong in young adults and they will ALWAYS find a way to get porn. I know I did when I was in my 20's.