not a furphy at all - in fact the primary objective for me fitting a Safari was due to dust rather than water-the standard air intake on a D2 Td5 is ridiculous for two reasons - firstly the size of the hole in the inner guard is puny; secondly it takes air from above the front wheel - great on dirt roads...not...
I've cut out a larger hole in my inner guard and have added my own large diameter flexi pipe connecting the end of the snorkel to the airbox. If anything, the car seems to go better - certainly not worse.
Interestingly, the current 4WD Action mag indicates (as tested) a significant fuel economy improvement with snorkel fitted - but of course this depends on the particular car and how restrictive the original air intake set-up is...

