No, they sit on top of the cylinders like a BMW boxer and the plug leads seal in much the same way. The first issue in deep water is when the bottom of the fan hits and throws water around. If you did swamp it, there is the trick of putting it in first gear and using the crankhandle to wind it out; of course you'll get your feet wet then. I'd say it probably takes 18" of water to kill it, minimum. Remember, they have high ground clearance anyway - unless heavily loaded! Also, many 4WD are pretend offroaders and I'm not including the "real" ones.
The inboard drums were dropped long ago (1981 for the 2CV and earlier on Dyanes) for inboard force-cooled discs which are a doddle to change the pads in. The drums are less fun but once setup they stay good for a fair while.
They're surprisingly expensive here too; rarity value is kicking in as more and more got scrapped due to terminal tinworm. The dashboard gearchange is actually very easy to use and doesn't clutter the floor. Just pretend it's a 5-speed and 1st is missing (that's where reverse lives).
I envy you the DS but not the cost of buying or running one. Voted the most beautiful car ever and also (recently) voted the most technically advanced car ever. If I could afford it, it'd be my number one pick.
The only issue I had in 10 years plus of ownership was the rear brake pipes. That's because later cars had rear seat belts and lost the access panel to the t-junction because of the belt-anchorage, making the job a nightmare. The kingpins are straightforward with a drift-set, the roller bearings rarely give trouble and the hydraulics are mainly unconventional in having no flexible hoses and using LHM fluid (which never needs changing). By French weirdness I think you probably mean Citroen. Unconventional is often innovative and that it was. Find me another engine that LJK Setright was unable to criticise and which can shrug off being run for 100 hours non-stop at maximum power and revs.
