Sure, it will put out the fire, but it will also have severe repercussions. The drastic temperature change may cause your grill to crack, not to mention the cloud of steam that would be released, resulting in your eyes watering.
We definitely don’t recommend pouring water over your grill because of the long hours you’ll have to clean up afterward, which would also include removing all of the charcoal and scrubbing the bottom of the grill to get rid of all the stagnant ash and water.