Freezing a fountain does something. All the following have been suggested:

• Destroys it and turns it into an ice square.
• Breaks it and creates pools before turning into an ice square.
• Sets a flag on it which indicates that it’s frozen; it’ll thaw eventually but it can’t be dipped into or quaffed from until then.
• Creates an ice devil (a water demon that got frozen) with the same odds as getting a water demon.