In butterfly, you want to stay as horizontal in the water as possible with hips high and chest low. In this video, two-time Olympian Chloe Sutton demonstrates a drill progression to teach swimmers how to maintain a proper body position through a whole race.
Timing is everything in butterfly. You can have the perfect technique, but if the "when" of your stroke isn't correct it will feel a lot harder (and slower) than it should be. Watch Chloe demonstrate some common mistakes and the proper timing for a fast and efficient butterfly stroke.
A very common issue in freestyle is when a swimmer's legs sink. This doesn't usually have much to do with how hard they're kicking. It's more about posture and core engagement. Watch this video and follow this drill progression to improve your body position for a faster and more efficient freestyle
Chloe Sutton - Sharing my experience of 20 years of competitive swimming including 8 years on the National Team and 2 Olympic Games.