There are two main things that swimmers should be focusing on every time they hit the water. The first is decrease our resistance in the water and secondly, increase our propulsion. Decreasing resistance is a major key to improvement. There are several forms of resistances we should be striving to eliminate from our swimming.
I once had a coach tell me that the best way to swim is to imagine yourself as twice the size you are. Over my career as both an athlete and coach, I've seen a lot of swimmers who swim like individuals half their size. What I mean is that they shorten their strokes, especially in Freestyle or as some call it Front Crawl, which causes them to lose out on some much efficiency in the water. One big idea that I try to get swimmers to understand is the notion of swimming like someone twice their size.
I've always felt that Breaststroke was seen as the lazy cousin to the other three IM strokes within the swim community. Some believe it to be the easiest stroke and the slowest. Unfortunately, I can't argue with you on Breaststroke being the slowest. Just the natural movements of Breaststroke make it slower and less streamlined than its counterparts, but this doesn't mean that it's for the lazy or is easy to do.
Body position is crucial to efficient swimming. It has the ability to affect your endurance and speed, especially as your body begins to fatigue. Body position is a key foundational element that coaches should cover early and often with their athletes. No matter how many years you've been swimming, you can always continue to work on and improve your body position and roll.
Learning out to maintain that momentum is something that takes time and needs to be a formed habit. Think of it like a car, if you are driving consistently at a 100 km/h for a long period of time, then your car will use less fuel to get you there, but if you are slowing down and then speeding up, you are going to use more fuel that way. Your body is the same way during a race. If you can find a consistent rhythm and pace that works for you, you'll use less fuel meaning you have more to give at the end of a race for that potential touch out or record breaking touch.
One issue I've faced over the years is knee pain among swimmers who swim breaststroke. Knee pain in swimmers, even though our sport is very low impact, is very real. This should never be ignored by an athlete or a coach. It has been documented that 73% of Breaststrokers and 48% of non-breaststrokers all suffer from some sort of knee pain. That's a lot of swimmers.
There is a misconception about the proper breathing for Butterfly. Many swimmers tend to come out of the water as much as they can when breathing in fly. This causes their hips to sink in the water meaning they have to expend additional energy to drive their hips back up to the surface. The result is usually a short pause between each stroke. That short pause, even if it's just for a split second, can throw off your entire rhythm.