Back before the installation of closed-circuit TV systems (and for many years afterwards), movies were shown on Navy ships. There was a service that sent them out to the ships, which then traded them around the Fleet. The prints were in 16mm format, they were almost all second-run movies. So if you had been deployed for a few months, they were new to your crew.
Movies were shown beginning at 2000 in three places: The Mess Deck, the Wardroom and the Goat Locker. For officers, unless you were the Captain, the XO or one of the no-loads (Supply, airdales on LAMPS ships), you didn't watch movies underway. If you were a pre-qual SWO, attending a movie was a sign to the XO that you didn't have enough to do, something that the XO would be sure to remedy for you in short order. If you had the time, you should have been working on your PQS, divisional paperwork, standing watches or getting some sleep.
In reality, every line officer below the XO, including Department Heads, skipped movies underway. If you had that much free time, you got caught up on sleep, which was a precious commodity underway, or you dashed off a letter or recording to your family back home. In port, if you didn't have duty, you went ashore rather than stay aboard the bloody ship and watch a movie. Unless, of course, you were in some Third World shithole of a port.
The movies themselves generally came on three reels, so there was always a break while the reels were changed out. I think it was SOP not to rewind them after viewing, so that the next user could see that the film was intact. But I'm a little hazy on that, as I didn't see too many movies. Most of them seemed to have the scratches that one would expect from a second-run grindhouse.
If porn was available, that would be shown after Taps. Wise captains conditioned the showing of porn under a "no complaints" policy- if one person objected, it was banned throughout the ship. (Which meant that it might still be shown in the Goat Locker.)
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