I've used ferry many times on my way from Hamburg Germany to Copenhagen, than to Sweden, and than back vice versa and so on ...
Was great fun, especially if its summer time and sothat you are allowed to sit outside and take a sunbath, otherwise on my winter trips the only solution was to stay cool against motion sickness which giant waves cause ...
The seats are very comfy, nice food, large windows to stare outside, even movies are shown not to get bored ...
There is a large option of ferry companies depending from which city / country you are arriving and its a strongly advised experience to try ... :)
Do what all Scandinavians love - cruise! The ferry to and from Oslo no longer docks right in the city centrebut still has a regular bus service straight to the centre. The ferry leaves for Oslo at 17.00 every day and arrives in Copenhagen around 9.00 in the morning. You can also get here by ferry from Poland (Swinoujscie) several times a week.
Crown of Scandinavia departs from Oslo to Copenhagen everyday, leaving Oslo at 5pm and arriving in Copenhagen at 9.15am. I personally think it was a boring ferry. I haven't been on many ferries, just Norwegian Wind to Alaska and this one. There's no way you can compare these two! I went to a club on Crown of Scandinavia and old people were dancing to 70's music. The best thing about it is probably the duty free shop :) The cabin can cost from $100 to 400 depending on what kind of room you want.
Check in Opens: 2 hours before departure
Boarding Starts: 1 hour before departure
End Boarding Ends: 30 minutes before departure
I went to Copenhagen from Oslo, and took an amazing
trip by ferry. It takes 16 hours from Oslo to Cop.
The huge ship named Queen or Prince provides all
kinds of cabin, restaurants, bars,entertainment and
Operated by DFDS Tel: (+45) 33 11 22 55.
To go to Norway, we went by ferry from Copenhagen/DK to Oslo/Norway (passing Helsingborg).
On this route you have the possibility of travelling either with CROWN OF SCANDINAVIA or PEARL OF SCANDINAVIA. The two biggest vessels of the DFDS Seaways fleet.
The ships alternate every day and depart at 17:00 from both Oslo and Copenhagen passing Helsingborg on the way. There are departures from Helsingborg to Oslo each day at 19:00.
For the curious ones, here are some data about the 'MS Pearl of Scandinavia':
Length: 176.8m Width: 29.6m
Cruising Speed: 21 Knots
No. of cars: 365
No. of passengers: 2,100
Year Built / Rebuilt 1989 / 2001
(c) photo of the ferry: http://www.dfdsseaways.co.uk/
Ferrys to and from Denmark are not first class but they are nice and safe enough to travel. Beware... there's a lot of drinking on board but there's also great food, and they show movies!