2007 Questions for all other cars low pick up power

Engine Mechanical problem
2007 Questions for all other cars 14000 miles

I have an indian car (maruti alto), 2007 model with 14000 mileage. As my friend was using it, he had opened the hood and poured water over the engine to wash it. I drove it after about 15 minutes of drying and I could feel the pick up power to be very less. Even at 2nd gear it can hardly pull my weight on an uphill road.
I did not notice anything unusual than that.

I let the engine dry up thoroughly and then drove it. Its back to normal now.

What could have been the problem. Is it safe to pour water over the engine just like that?

thanks.