Hey there,
You're going to need to open the device up and clean the effected components. I would highly recommend taking a look at our [[Laptop is Liquid Damaged|Laptop is Liquid Damaged]] and [[Electronics Water Damage|Electronics Water Damage]] Wikis and the the [guide|95280|iPhone Liquid Damage Repair Guide]. If the battery was effected by the water, then you are going to need to replace the battery.
Best of luck to you!