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

Overview

The Garmin Forerunner 965 is a dedicated endurance training tool built for marathoners, triathletes, and ultra-distance athletes who want deep performance analytics and multi-day battery life. The Apple Watch Ultra 3 targets the same athlete but comes from the opposite direction: a premium smartwatch that has earned genuine sports credentials rather than a sports computer that added smartwatch features. The core trade-off is battery life and training depth versus ecosystem integration and day-to-day versatility.

Specs at a glance

Price tier: Forerunner 965 around $599; Apple Watch Ultra 3 at a higher premium price point
Weight: Forerunner 965 at 53g; Apple Watch Ultra 3 at 61.4g
GPS battery life: Forerunner 965 up to 31 hours standard GPS, 110 hours expedition mode; Apple Watch Ultra 3 approximately 18 hours standard GPS, 72 hours low-power mode
Smartwatch battery: Forerunner 965 approximately 23 days; Apple Watch Ultra 3 designed for daily charging cycles
Display: Forerunner 965 1.4-inch AMOLED 454x454; Apple Watch Ultra 3 always-on microLED with flat sapphire crystal
Heart rate sensor: Both use wrist-based PPG optical sensors for blood volume measurement; neither uses electrical ECG for continuous HRM during workouts
Water resistance: Both rated to 100m; Apple Watch Ultra 3 adds EN13319 dive certification
Open-water swim GPS: Apple Watch Ultra 3 outperforms Forerunner 965 directly in benchmark testing

GPS and tracking accuracy

Both watches use dual-frequency multi-constellation GNSS, so raw satellite acquisition is competitive. In open-water swim GPS accuracy, the Apple Watch Ultra 3 beats the Forerunner 965 in direct testing, a concrete result that matters for triathletes where wrist GPS during swimming is typically the weakest link. In satellite connectivity benchmarks, the Ultra 3 also beats the Garmin Fenix 8 across multiple metrics, which puts it at the top of the category in raw connectivity terms.

On road running courses, the Ultra 3 performs well in structured benchmark testing. The Forerunner 965 received firmware updates that addressed GPS drift under heavy tree cover, which previously corrupted trail data. That fix is in place, making the 965 reliable on technical trail routes where dense canopy causes problems for many multi-band watches. For road and track use, both watches are accurate enough that the difference will not affect training decisions. For open-water swimming, the Ultra 3 has a measurable edge.

Battery life

This is where the two watches diverge most sharply. The Forerunner 965 runs 31 hours in standard GPS mode and up to 110 hours in expedition mode. In real-world endurance use, a 77-mile ride test confirmed the 965 keeps pace with competitive devices over long durations. Full Ironman distance, 100-mile ultra runs, and multi-day adventures are all within its range without a charger.

The Apple Watch Ultra 3 offers approximately 18 hours in standard GPS mode and 72 hours in low-power mode. That 18-hour figure is enough to cover a half-Ironman with careful management, but a full Ironman is a hard stop. For any event pushing past 15 to 16 hours of active GPS use, the Ultra 3 requires either a mid-race charge or the low-power mode that reduces tracking fidelity. The Forerunner 965 has no equivalent constraint at standard distances.

For athletes: who wins?

Road running and marathons: Forerunner 965. Deeper training analytics, real-time stamina data on the map screen, and no battery anxiety for long training days.
Trail running: Forerunner 965. The firmware-updated GPS handles tree cover well, battery life covers ultra distances, and the expedition mode extends to multi-day efforts.
Triathlon (sprint to half-Ironman): Apple Watch Ultra 3. Superior open-water swim GPS accuracy is a direct performance advantage, and 18 hours covers these distances comfortably.
Full Ironman and ultra-endurance: Forerunner 965. 31 hours of standard GPS is non-negotiable for events in this range. The Ultra 3 cannot complete them on a single charge in standard mode.
Recovery and daily tracking: Apple Watch Ultra 3 if you live in the Apple ecosystem. The smartwatch experience is superior for daily use. Forerunner 965 wins on battery, lasting weeks between charges without the daily charging habit the Ultra 3 requires.

Verdict

For most serious endurance athletes, the Forerunner 965 is the stronger choice. Its battery life advantage is not marginal; it is the difference between finishing a full Ironman or an ultra and not finishing it on a single charge. Training analytics and on-device data depth are also stronger out of the box.

The Apple Watch Ultra 3 makes a genuine case for triathletes competing at sprint to half-Ironman distances, where its open-water swim GPS accuracy is a measurable advantage and its battery is sufficient. It is also the right choice for athletes deeply embedded in the Apple ecosystem who want one device for sport and daily life.

Buy the Forerunner 965 if you race long, train on trails, or want weeks of battery life without daily charging. Buy the Apple Watch Ultra 3 if open-water swim accuracy matters most to you, your events stay under 15 hours, and you want a world-class smartwatch that also handles serious sport.