River boats and the like don't have to deal with waves in any meaningful way. The draft of a river boat is best as shallow as possible - this is not at all good for dealing with open water where swell, wind and waves dictate a much more robust and different handling hull.
The precise differences are absolute - completely dictated by the use of the boat, and the conditions it will face in that use.
Every boat design is specifically built to answer those requirements, and that is why there are so many varied styles and arrangements of hull type. You will also notice that in a given area the boats will tend to be quite similar - that is because the unique conditions in any given location tend to favour one type above all others.
So for a trip down the Thames, you would pick a river boat, of which there are many types, from liveaboards to barges to canal boats and even robust rowing and sailing dinghys. Once you know what you are doing, you can go to the area and ask advice of the locals - who would rather see you set up correctly than have to rescue you.