Built for the Long Haul
Apple's Ultra 3 targets serious endurance athletes who need reliable GPS tracking, multi-day battery life, and health metrics that actually inform training decisions. I wore it through a full marathon, a 100-mile cycling event, and an Ironman 70.3 to see if it can replace dedicated sport watches.
GPS Accuracy
The dual-frequency L1/L5 GPS is the most accurate GPS I have tested in any smartwatch. During the marathon, the recorded distance was 26.24 miles versus the certified 26.22, a 0.08% error. In urban canyons with tall buildings, the Ultra 3 maintained track accuracy where competing watches drifted by 15-20 meters.
Open Water Swimming
During the Ironman 70.3 swim leg of 1.2 miles, GPS tracked within 30 meters of the actual course. Water submersion did not affect signal acquisition and the watch reconnected within 5 seconds of each arm surfacing.
Battery Life Under Load
- Marathon (4h15m GPS + HR): 82% remaining after
- Century ride (6h GPS + power meter): 61% remaining after
- Ironman 70.3 (5h42m GPS + HR): 68% remaining after
- Full day with always-on display: 36 hours total
Health Metrics
The new blood pressure trend feature showed consistent readings within 3 mmHg of a clinical cuff. VO2 Max estimation tracked closely with lab-tested values. Sleep tracking accuracy for REM and deep sleep stages matched reference devices within 10%.
Compared to Garmin Fenix 8X
The Fenix 8X offers more training metrics and longer battery life at 48+ hours GPS. But the Ultra 3's smartwatch features including cellular, Apple Pay, Messages, and ecosystem integration are significantly better for daily use.
Verdict
If you want a watch that excels at both endurance sport tracking and daily smartwatch tasks, the Apple Watch Ultra 3 is the best dual-purpose wearable available.