What “dry land” exercises are useful for swimming (butterfly/cross-stroke)?
Butterfly uses a lot of your core, so try different types of crunches and Pilates. Technique also plays a pretty big part of butterfly, so make sure you’re making the most of your stroke and not flailing your arms. Make sure your arms, head, and legs are coordinated. For example, when your head is down, your butt is up. You take a breath when you start your pull. That kind of stuff. Butterfly also requires shoulder strength and back strength. Work on those. Butterfly is, in my opinion, the most tiring stroke out there. Just keep training and you’ll get better!