Murky vs Rexxar
Rexxar is a 'bear' to handle. Ideally you would just ignore Misha the bear and attack Rexxar. The problem is Misha's stuns. With Murky if you get stunned you die. Rexxar can also kill your puffer fish easily.
Fish Tank does not really help here becuase the problem is not damage. The problem is stuns. Best option here is to switch lanes.