SWMBO had this problem, or something similar on her Td5 90 - white smoke and ran like a bag of bolts.
Booked it in to the local stealer - somehow, even with a snorkel, the air filter box had a load of water in it!
It had also knacked the Air Flow meter, but a new AFM and a filter has cured the problem - still not a clue on how the water got in there in the first place tho
HTH
Regards, Chris