water waves over the exhaust tip has pressure to push water in exhaust, if yr exhaust is over the water level, yr safe frm exhaust problem
engine will stall when exhaust go out, you need higher exhaust pressure to keep water out frm getting in exhaust.
engine rpm depends on how much water push you require, dnt go fast in water, its getting in engine bay too, messing up wires and other stuff.
2ndly the half clutch pressed driving in water ruins the clutch plate. experts dont touch clutch padel in water,, enter deepwater in 1st gear, maintain a speed ,,,keep praying yr car or car in front doesnt stall.
if possible let the water level on road drop to resonable level, better wait outside then stuck in it with water making carpet wet..
too much excitment to drive in deep water doesnt pay off
if its a regular crises in yr area,,, lift yr car by changing suspension or buy jeep,, high ground clearance cars can not go fast but they can go through difficult areas