Water in the fan box for the heater.
If you have AC you need to clean the drain valve in engine bay. with engine cold reach down the back of the engine to near where gear linkage rod comes out and there is a rubber tube, squeeze it and water should drain out.
It is not good to have water in there, the lower fan motor bearing will be sitting in the water which will wash out the lubricant and eventual seize up. Also the resistor pack for the fan motor sits very low down near the fan and could also get wet. Worse case it will catch fire. Not so common on the Corsa C but more common on the Zafira B and Corsa D.