underwaterDepth: HealthKit quantity type
HKQuantityTypeIdentifierUnderwaterDepth · read from Apple’s documentation on 2026-10-02
HKQuantityTypeIdentifier.underwaterDepth (Objective-C HKQuantityTypeIdentifierUnderwaterDepth) is a HealthKit quantity type in Apple's "Diving" group. Apple's abstract: “A quantity sample that records a person’s depth underwater.” Apple's discussion says its samples use length units and measure discrete values, so in HKStatisticsQuery it takes .discreteAverage, .discreteMin or .discreteMax. It is available from iOS 16.0 and watchOS 9.0.
What Apple says underwaterDepth is
A quantity sample that records a person’s depth underwater.
Apple’s abstract, quoted from its underwaterDepth reference page, read 2026-10-02. Apple’s discussion of the type runs 40 words.
- Swift
HKQuantityTypeIdentifier.underwaterDepth- Objective-C
HKQuantityTypeIdentifierUnderwaterDepth- Family
HKQuantityTypeIdentifier- Apple's topic group
- Diving
- Group page
- Environment, hearing and diving
- Apple's reference
- underwaterDepth on developer.apple.com
Availability
The versions Apple’s documentation data gives for underwaterDepth, platform by platform, as read on 2026-10-02.
| Platform | Introduced | Deprecated |
|---|---|---|
| iOS | 16.0 | — |
| iPadOS | 16.0 | — |
| Mac Catalyst | 16.0 | — |
| macOS | 13.0 | — |
| visionOS | 1.0 | — |
| watchOS | 9.0 | — |
The rest of that release: HealthKit Types Introduced in iOS 16.
Sum or average, and in which units
Apple states both of these in the prose of the type’s discussion, not as properties, so they are derived from Apple’s sentence and the sentence is shown with each.
Aggregation style
discrete — in an HKStatisticsQuery, use .discreteAverage, .discreteMin or .discreteMax. Apple’s sentence:
Underwater depth samples use length units (described in ) and measure discrete values (described in ).
Unit family
length — every type in this family is on the HKUnit reference.
Apple states it in the same sentence as the aggregation style, quoted above.
Empty parentheses and a dangling “described in” mark links in Apple’s sentence to other documentation pages: the generator keeps the sentence’s text, not its links, and the quote is left as stored rather than repaired.
Can apps write underwaterDepth?
Apple’s documentation for underwaterDepth does not state that its samples are read-only. Apple states read-only status only in prose, and its silence is not a statement either way, so this page makes no claim that apps can save it.
On Android Health Connect
No verified Health Connect counterpart. The cross-platform matrix pairs only metrics checked against both Apple’s and Google’s documentation, and underwaterDepth is not among them. A similarly named Health Connect record may exist, but a name match is not a verified mapping.
Questions
- Should I sum or average underwaterDepth in HealthKit?
- Average it, or take its minimum or maximum — do not sum it. Apple's documentation for underwaterDepth describes it as measuring discrete values, so an HKStatisticsQuery over it takes .discreteAverage, .discreteMin or .discreteMax. Apple's sentence, as read on 2026-10-02: "Underwater depth samples use length units (described in ) and measure discrete values (described in )."
- Which unit family does Apple give underwaterDepth?
- Length. Apple's discussion of underwaterDepth says its samples use length units: "Underwater depth samples use length units (described in ) and measure discrete values (described in )."
- Which iOS version added underwaterDepth?
- iOS 16.0. Apple's availability data for underwaterDepth lists iOS 16.0, iPadOS 16.0, Mac Catalyst 16.0, macOS 13.0, visionOS 1.0 and watchOS 9.0.
Sources checked
- Apple — HKQuantityTypeIdentifier.underwaterDepth · read 2026-10-02
- Apple — HKQuantityTypeIdentifier · read 2026-10-02
Apple’s abstract and sentences are quoted for identification; the page layout, the capsule and the cross-platform pairing are AIFitnessAPI’s. Generated from Apple’s documentation by scripts/fetch-healthkit-identifiers.mjs, not typed by hand — the same data as the full identifier table.
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