It was like 15 hours. Dinner, hang out for a bit, sleep, breakfast, arrive.

It was the first cruise ship I'd ever been on and was very small (Viking line) — like 6 decks. No pool, but 2 hot tubs down below.

I have also taken ferries from Goteborg, Sweden to Frederikshavn, Denmark a couple of times and also one from just north of Copenhagen into Sweden. The first one was like 2 hours. The other one was more like 30 mins.