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Apple Watch Ultra Limitations for Diving
The Apple Watch Ultra is the only Apple Watch with a depth gauge rated to 40 meters. But it has limitations that every diver should understand before using it underwater.
Depth gauge: hardware facts
The depth gauge is rated to 40 meters (EN 13319 water resistance, not dive computer certification). It measures water pressure and converts to depth. Accuracy depends on water salinity and temperature. DiveOne reads this sensor at 1 Hz — the maximum rate Apple provides to third-party apps.
Temperature sensor
The water temperature sensor provides readings with approximately ±0.5°C accuracy. It measures the temperature at the Watch case surface, which may lag slightly behind ambient water temperature during rapid depth changes.
Battery under water
Continuous depth tracking with screen active uses approximately 10–15% battery per 60-minute dive. This varies with screen brightness, haptic frequency, and water temperature (cold reduces battery performance). DiveOne recommends starting dives with 30%+ battery.
What the Watch cannot do
The Apple Watch Ultra does not have: a gas mix sensor, a compass reliable at depth, cellular connectivity underwater, or any decompression calculation capability. DiveOne works within these hardware constraints — we track what the sensors can measure, and we're transparent about what they can't.