Butterfly

The key to swimming butterfly long distance is a strong kick. Don't get me wrong, it is important in sprints, too, but when you are trying to do a 100 yard or 200 yard fly your kick needs to be strong and timed perfectly. If you rely on your arms too much you will die. Remember to follow through all the way down to your suit.

I'm not a very good swimmer of Butterfly but here's what my coach taught me. Get a kick board and practice your dolphin kick. It's called dolphin kick because you'll need to imitate the way a dolphin moves its tail. For every kick you do if you but raises up from the water then your kick is string enough to support your arm movement. After the arm takeoff and during the time you take your arm underwater you must push your hips forward to intensify your kick, this movement will raise your butt from the water. I hope you understood what I'm trying to say. Look for some techniques on the internet, you may find instructions with drawing, all you need to do id to follow them and practice a lot. Good luck!

As they say, "constant practice makes perfect." So go ahead, practise some more and you might learn the tricks by yourself. When you get stronger, perhaps you can persist to swim farther distance and faster.