Okay, this is pretty weird, but for me the hardest swimming stroke is the front crawl, or just commonly called freestyle. This is the first stroke that I've learned, and the one that I have been doing the longest. But until now, I still can't do it perfectly. Either I don't do it right or I overdo it. I overdo the hip rotation and the stroke itself. I don't know what's wrong or what simply to do. I consider butterfly stroke to be easier, far easier that's why I love doing it, but it's harder to develop endurance on it. It's easier to do, but it's the hardest to swim continuously without stopping.