This remembers me on the last trip we made to the north this last winter. On a rainy day a friend caught a really big mud hole that apparently seemed just 1" deep. He sucked water with mud though the intake and it hit the filter so hard that it altogether gone inside. The mesh on the MAF stopped it all and saved is engine. Such things are possible, and I think very provable becouse years ago I experienced some hydrolock in my Astra GSI in simmilar conditions.
As the GA TB not having the mesh... god knows. My father, that was some VIass on Opel (Err Vauxall) told me that some stupid dude implemented improvements on the Opels productions lines to save some bucks and gained reputation an status. He ordered shorting the engines harness wires more than an inch, and then sensors were unpluggin now and then on the road.
I must say... don't argue for such small things boys. 
