Apple Watch Series 10 failing to track Breaststroke (Pool Swim)

This is a genuinely frustrating situation and your frustration about the longevity and repair cost is completely understandable.

On the technical side: breaststroke detection on Apple Watch relies heavily on the accelerometer picking up the specific arm movement pattern. The Series 10 uses a thinner, flatter design compared to previous models, and there have been reports from other users that this particular hardware revision handles breaststroke detection less reliably than freestyle, since breaststroke has a very different arm trajectory at the wrist.

A software wipe not resolving it does lean toward a sensor calibration or hardware issue, though it's hard to say definitively. A few things worth trying before accepting the repair quote:

1. When you swim breaststroke, try wearing the watch on the opposite wrist if you haven't already. The orientation and which wrist you wear it on can meaningfully affect how the accelerometer reads your stroke.

2. In the Watch app on iPhone, under Workout settings, make sure the wrist setting (dominant vs non-dominant) is set correctly for your actual wearing wrist. A mismatch can throw off stroke algorithms.

3. Try a full watchOS reinstall using Recovery mode if possible — deeper than what the Apple Store typically does in-store — though this may require contacting Apple directly.

On the repair cost: it's worth calling Apple Support (not the store) and escalating the case. A device less than two years old that's stopped accurately tracking a core advertised health feature is a reasonable basis for a customer satisfaction exception, even without AppleCare. It's not guaranteed, but it's worth the call and asking specifically for an exception review given the circumstances.

Did you install the latest watchOS 26.6 around this time? This could have been an included software fix in the update.