This video from Effortless Swimming is a great example of 3 effective drills for developmental and advanced competitive age group swimmers.

One Arm Free:

Streamline first like normal, then, put one hand next to your side in soldier. Swim Freesytle with the other hand, breathing on every stroke and turning your face towards the arm in soldier, or your “weak side.”

Swim left arem down, and right arm back. Will always breath looking at the same side of the pool.

Long Dog:

I’m not as familiar with this drill, but it looks like a modified slow arm stroke with prolonged position 11 glide where or a extra kick while slowly recovering underwater.

Sculling:

Pushing the water in and out while keeping the arms mostly above or in front of the shoulders helps teach the “feeling” of the water. It will encourage swimmers to remember and focus on the “catch” or grabbing the water and making the body move.

*I would avoid sculling for beginners in Developmental programs. Some small attempts might be effective but longer 25’s or sets of sculling often isn’t productive and will lead to bad habits.

If you REALLY want to scull, do this challenge instead: