Entertainment is what you make or bring. Ships have a movie channel (sometimes more than one) but game consoles, books, VCRs/DVDs, cards, and sleep are more common. Engineering is especially prone to sleep when they can grab it underway. Personally, I did a bit of creative writing, some gaming, a lot of smoking, and averaged about 4 hours sleep a night (often not in a row) and one meal a day since, between working, watch, drills, and such, there wasn’t much time for entertainment except on Sundays (8 hour workday instead of 12, though I still had watch).
Of course, you likely won’t go into Engineering so you may actually have to worry about entertainment. And like I said, it’s pretty much whatever you bring, and considering how much storage space you will have, whatever hobby you have will have to fit into a seabag, minus whatever room your civilian clothes take up. And it it requires a power adapter/cahrger (like a laptop or a gaming console) then there are special rules for that; say high to the guys in Electrical Safety.
I also recommend learning to play cards and/or Dominos in case you want to do something non-solitary.