It's the HT electrics that have spark gaps (like the dizzy contacts) that are badly affected by water.

On newer stuff though you do need to think about the injectors, alternator and probably who knows how many sensors. Modern common rail diesels have lots of electrical stuff that probably doesn't like water but the older "mechanical" diesels have no problem.

Again I am not an expert but I tend to agree with classic keV.modern diesels have approximattely the same electric staff with the petrols cars.i could say there is no difference.if you going to take your car for a deep ride it needs to be well equiped what ever the engine is.

most use 200 or 300 tdis as few electrics,which is what most mean when talking about diesels,you wouldnt want to take a new vehicle in extreme conditions as earlier trucks

BUT its still like a 100:1 ratio of problems with ignition vs. everything else

my engine is an efi, you could dunk it til your blue in the face and those 12v high current electrics will keep on contacting, but the very high voltage low amperage electrics on the igntion system cannot arc across a wet gap, or you get tracking elsewhere etc.

the difference is the amperage, igntion is very low current, thats why theres many water problems.

ok i agree if you submerged two engines completely (forgetting the ignition for this example), the petrol would stop running first because EVENTUALLY an electrical item would succumb to water problems, but my guess is it would take a suprisingly long time.

cheers