I just swam 1400m with the Apple Watch Ultra 4 and Garmin Fenix 9 Pro: Here’s which watch came out on top, and it wasn’t the one I was expecting

In a recent test comparing the Apple Watch Ultra 4 and Garmin Fenix 9 Pro, both high-end fitness trackers were submerged in a 1,400-meter swim to measure their accuracy and usability. Both watches use an internal accelerometer and gyroscope to track arm pulls and calculate strokes per length, stroke rate, and offer a SWOLF score, which gauges stroke efficiency.

Both models are waterproof up to 10 meters, automatically detect strokes, and can provide SWOLF scores. However, their usability differs due to design changes – the Garmin Fenix 9 Pro features five leakproof buttons on the left and right side, offering smooth navigation underwater, while the Apple Watch Ultra 4 locks the screen when submerged, requiring users to deactivate the Water Lock feature to stop tracking the swim.

During the swim, the results revealed that the Apple Watch Ultra 4 recorded a distance of 1,440 meters, while the Garmin Fenix 9 Pro logged 1,480 meters, a 40-meter discrepancy, or approximately two lengths of a 20-meter pool. Despite the slight difference in distance, both watches proved to be accurate overall. The Apple Watch Ultra 4 also proved to be more precise in stroke analysis, accurately categorizing the swim as Freestyle, Breaststroke, and Mixed without any inconsistencies, while the Garmin Fenix 9 Pro occasionally struggled to differentiate between strokes.

The Garmin Fenix 9 Pro offered an added bonus: compatibility with a compatible HRM Swim chest strap for enhanced swimming data.