Apple Watch Ultra 3 vs Garmin Forerunner 965: Which GPS Watch Wins?

Overview

The Apple Watch Ultra 3 is a premium smartwatch that doubles as a serious sports tracker, built for athletes who want one device for training, racing, and daily life. The Garmin Forerunner 965 is a dedicated endurance training tool that happens to have smartwatch features, not the other way around. At similar price tiers, they serve overlapping but distinct user profiles.

The Ultra 3 leads on smartphone integration, open-water swim GPS, and display quality. The Forerunner 965 leads on battery life, training analytics depth, and overall endurance sport utility.

Specs at a glance

Weight: Ultra 3 at 61.4g vs Forerunner 965 at 53g
GPS mode battery: Ultra 3 at ~18 hours standard GPS vs Forerunner 965 at ~31 hours GPS mode
Extended GPS battery: Ultra 3 at 72 hours low-power mode vs Forerunner 965 at 110 hours expedition GPS mode
GPS chipset: Both use dual-frequency multi-band GNSS with multi-constellation support
Sensors: Both include wrist optical HRV, SpO2, skin temperature, and barometric altimeter
Display: Ultra 3 microLED with flat sapphire crystal vs Forerunner 965 1.4-inch AMOLED at 454x454
Water resistance: Ultra 3 rated to 100m with EN13319 dive certification vs Forerunner 965 at 10 ATM (100m)
Price tier: Ultra 3 sits significantly higher; Forerunner 965 at approximately $599

GPS and tracking accuracy

Both watches use dual-frequency L1/L5 GNSS, which puts them in the top tier for satellite acquisition. In direct testing, the Ultra 3 outperforms the Forerunner 965 specifically in open-water swim GPS accuracy, a meaningful win for triathletes where wrist GPS during swimming is historically unreliable. In satellite connectivity benchmarks, the Ultra 3 also beats the Garmin Fenix 8, placing it at or near the top of the category for raw acquisition performance.

The Forerunner 965 received firmware updates that addressed GPS drift in dense forest environments, which had previously caused pace and distance errors on technical trail routes under heavy tree cover. That fix matters for trail runners. On road running, both watches perform at a high level, and the gap between them is small in practice.

For open-water swimming, the Ultra 3 has a concrete accuracy edge. For trail running under tree cover, the Forerunner 965 with updated firmware is the more proven option.

Battery life

This is where the two watches separate clearly. The Forerunner 965 offers 31 hours in standard GPS mode versus the Ultra 3's approximately 18 hours. That difference is decisive for full Ironman racing, which runs 12 to 17 hours, and for ultra-distance events beyond that. The Ultra 3 covers a Half Ironman with careful power management. It does not reliably cover a full Ironman without the low-power mode, which reduces GPS accuracy and feature access.

In expedition GPS mode, the Forerunner 965 reaches 110 hours versus the Ultra 3's 72 hours in low-power mode. For multi-day adventures, the gap widens further. In a real-world 77-mile cycling test run alongside the Ultra 3, the Forerunner 965 demonstrated its endurance advantage in direct comparison. For athletes whose events run longer than 18 hours, the Forerunner 965 is the only practical choice of the two.

For athletes: who wins?

Road running and marathons: Forerunner 965. Deeper training analytics, lighter on the wrist, and longer battery for back-of-pack marathon runners or back-to-back training days without charging.
Trail running: Forerunner 965. The GPS drift fix for dense forest environments is directly relevant, and 31 hours of GPS covers most ultramarathons without switching modes.
Triathlon (sprint to Half Ironman): Tie. The Ultra 3 wins on open-water swim GPS accuracy, which is a genuine advantage. The Forerunner 965 wins on battery for longer events and training analytics depth. Choice depends on whether swim accuracy or training data matters more.
Recovery and HRV tracking: Forerunner 965. Garmin's training load, recovery advisor, and stamina data tools are more developed than what the Ultra 3 offers through watchOS, particularly for athletes who structure training around Garmin's ecosystem.

Verdict

The Garmin Forerunner 965 is the better endurance sports watch for most serious athletes. It is lighter, lasts nearly twice as long in GPS mode, and provides deeper training analytics built specifically for endurance sport. The Apple Watch Ultra 3 is the better device if you want one watch for everything and your longest single-session event stays under 15 hours. The Ultra 3's open-water swim GPS advantage is real, but it does not offset the battery gap for full Ironman or ultra-distance athletes.

Buy the Forerunner 965 if you train and race seriously, particularly at distances beyond a Half Ironman or on trails. Buy the Ultra 3 if you want a premium daily smartwatch that can also handle triathlon-distance racing without compromise on the swim leg.