I would not have known about the cold water shower if you had not told me, I will take your advice on the youtube vids, maybe then I'll stop asking daft questions, thank you.[To help you get a feel for what’s what there are plenty of guides/ tours on YouTube - some better than others. Also download the Mercedes V Class / Marco Polo Guide/ operator‘s manual and configurator.]
In the UK Marco Polo campervans i.e. with kitchen, sink, wardrobe etc., have the shower outlet. Don’t get too excited though it’s a cold water outlet for connecting to a flexible spray nozzle - see MP accessories. In cold climes UK good for washing boots, dog etc unless you are really hardy!
The Horizons have three rear bench seat/ bed and no kitchen / sink or shower outlet.
What would be nice is to have an MP Horizon (i.e. no kitchen wardrobe etc) with double as opposed to triple rear seat so that you could fit in skis or surf board down the side.
Mercedes are missing a trick.
I would be interested to know if the campervan double rear seat could fit in the Horizon.