The Hull to Amsterdam ferry is mostly made up of economy cabins that have the bare essentials. The rooms come with 2 single bunk beds and a small shower/toilet room. The rooms are small and more often than not the heat controller doesn’t even make a difference.
In my opinion, the rooms are exactly what they say on the tin, economy class. Still it’s a cheap way to get to Amsterdam, it just takes a little longer.
There are ways though of making the beds just a little bit more comfy on the ferry. First of all you have to assess the space situation. There’s also a ladder and a small stool to take into account here, plus your luggage so space is gunna be tight. It can still be done though!
Next thing is to move the ladder and small stool next to the door. After you’ve lumped these across the room, the next thing is to remove the mattresses from the bunks. This might sound crazy, but it’s much better than sleeping in those pesky bunks, Especially if your a couple.
Lay the mattresses on the floor to make a double bed, it’s a tight fit as you push the mattress under the bottom bunk. But it does fit. Now all you have to do is lie the covers over the top and spread the sheets out and the jobs done.
You now have a comfy double bed instead of two uncomfortable bunk beds.
As for the luggage,stool and ladders. Well you can either open the top bunk and put them there,place them by the door, or put them in the shower. Each of these have their drawbacks, but each have their benefits too.
If you decide to do the above to your cabin beds, make sure you at put the mattresses back in some kind of order before you leave. It’s the polite thing to do. 
Here’s some pictures of the rooms on the ferry from Hull to Amsterdam.
