Swimming is a little behind the curve when it comes to strength and conditioning. It's like how baseball was before Eric Cressey and others devoted much of their time to improving it.
When you do a search of swim dryland exercises or look on social media, you always find the same thing - exercises that look like swim strokes.
At the surface, this seems like it would make sense. Mimic the exercise on land, but add weight or a band to it, and it should improve the stroke.
As it turns out, doing a stroke in the water is very different from doing it on land. When you're buoyant and pulling yourself through the water, it's not the same as laying on your back and pulling bands, for instance.
A much better alternative is to determine what's required for a stroke. Look at the range of motion, joint action, strength needed, etc. of that stroke, then work to improve that. It takes a little higher-level thinking, but it will improve your performance to a greater degree.
At Achieve, we thoroughly evaluate every athlete, then look to see where they may need improvements. We compare their limitations to the needs of swimming. This is a much better process for improving performance.