The 2.0i 8 valve could go in as deep as half way up the doors (almost the top of the bumper) but if the fan started spraying water around the engine bay it stopped the engine!
Carry a spare fan belt and when you've GOT to go through water stop the fan and hook it on to something with the fanbelt.
Or if you have electric unplug it!
The 16v engines were better because a lot of the electrics were covered...
Make sure the electrics are coated with something like a silicone sealant...
Don't go over the bumper depth though because your air intake is there.
It's the electrics which let down the petrols..
Mind you I wouldn't go any deeper in my diesel now because I still have the air intake in the same spot until I get a snorkel.. And I've got a leak to fix in the gearbox tunnel where the tunnel hole for the gearsticks had to be make slightly longer.. Got to seal that

Anyway, have a play and try it out.. go through shallow water at first, at least you know whether or not it will stop with water on the electrics. You could even open the bonnet while it's running (after spraying silicone sealant around liberally) and using a hosepipe gently spray some water around and see how it reacts.
Just remember where the air intake is and if it stops in the middle of the water and the water is over the height of the bumper DO NOT START THE ENGINE until you have checked everything out. If the filter is wet then there may be water in the engine.. take out the spark plugs and turn the engine over to pump out any water... then give it a little while to dry out, put back the plugs and start it, should be fine.
I'm sure someone else will elaborate a little further on this.
Si