We did exactly that two years ago. Hammock is cheap, but be aware, you have to keep an eye on your luggage all the time, it can’t be stored. So even while you are asleep, people can have a quick fumble with your backpack.

Your own cabin is therefore recommended. We had one, tiny, hot, but a bunk bed and just enough room to store two backpacks, it was well worth the extra cash. The airco we never saw…

Be aware that there are many people trying to mediate or actually sell you your hut when in Manaus. Make sure you do not get conned. We were promised a double bed, but ended up in a bunk. By the time we were aboard, there was noone to complain to, we couldn’t do anything about it anymore.

We did buy a hammock on the dock though, which was useful, as in daytime just sitting on the boat is not very comfortable at all. A hammock is.

Have fun.