How to counter Fizz
Let us take a look on how to beat Fizz. We will look at champions who are strong against Fizz and who are weak against Fizz. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Mid champion who counters Fizz. You can already win in champion select with the right counters for Fizz. If you want to know how to counter Fizz then you need to take into account the best picks vs Fizz and the worst picks vs Fizz. This Fizz counter data is based on matches played by Pros on patch 14.16 and previous ones. It is important to see whether Pros counter picked Fizz or whether they played as Fizz.
Champions used by Pros to counter pick Fizz
Looking at the matches from Pros (see table Pros counter picked Fizz) we can see that they picked 
Corki most often to counter pick Fizz. The matchup Corki vs Fizz occured 14 times. Fizz has 5 wins and 9 losses in this matchup. Learn how to counter pick Corki to get another perspective on the data.
Lane outcome for Fizz
When looking at Fizz counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Fizz. The lane outcome of Fizz consists of three outcomes: Win, Loss or Draw. Let's take a look of Fizz lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Fizz.
Conclusion
Analyze the available data and learn how to beat Fizz. To master Fizz take also a look on Fizz builds and runes for Fizz. Good luck, Summoner!