Temp gauge not working?

Just because it put some water in the overflow doesn't necessarily mean it overheated. Did you top it off between the last time you drove it and when you took it out for the latest drive? Could have just been some excess coolant.

Warm the car up and check the actual temperature and compare it to the gauge reading. Or check it against a known gauge. At this point it could be nothing (excess coolant leaving the overflow), a bad sender, a bad connection, or a bad gauge. Time to eliminate possibilities.

I run a stock and an auto meter temp gauge on my car off two separate senders right next to each other. The stock gauge is more representative of the actual temperature. The auto meter sender works fine and drives my fan controller (which also will tell me the temp), but the auto meter gauge itself reads hot. Aftermarket isn't always better.