By PulsHealth. Updated
Research reviewed .
What does underwater depth measure?
Underwater Depth is a discrete length measurement below the water surface. Apple documents automatic recording during dive sessions on Apple Watch Ultra. A sequence can describe the depth profile of a session; adding depth samples does not produce distance traveled. Apple defines the type.
Which device limits matter?
Current Apple Watch guidance covers Ultra models and Series 10 or later, excluding SE 3. It gives maximum Depth-app limits of 40 m for Ultra and 6 m for Series 10 and later. These equipment limits are not a typical range for user data or a statement that a dive is safe. The Depth app does not provide decompression or gas-analysis functions.
| Item | What it tells you |
|---|---|
| Depth sample | A recorded distance below the surface |
| Session maximum | Deepest observed value, subject to coverage |
| Device limit | Equipment specification, not a personal target |
| Gap in the series | Missing detail; it does not prove surfacing |
Why might a dive profile have uneven spacing?
Apple notes that samples may be condensed or coalesced. A saved row is therefore not necessarily one original sensor observation. Inspect start/end times, durations and session coverage before comparing recording intervals. An unweighted mean can overrepresent the periods with more saved rows; duration-aware summaries need a stated treatment of gaps and condensed samples.
Apple's Depth app can combine another descent within 10 minutes into the preceding dive if that session has not been ended. Session identity should come from the source's records, rather than a fixed gap rule invented from sample timestamps.
What comparisons help explain a session?
A depth profile beside water temperature can show recorded environmental changes when sources and intervals align. Swimming distance answers a different question. Neither an overlapping workout nor a deep sample establishes complete dive history, equipment suitability or decompression status.
What did the coverage review find?
The reviewed 365-day example-data window contained no samples, stored aggregates or workout-series points for this type. Value distributions, unusual readings, recording cadence and related-data comparisons could not be measured. No empirical figure is presented; missing database rows do not establish missing records on the phone.
Does PulsHealth collect this type?
This identifier is part of HealthKit, but is not listed in the current PulsHealth sync catalog. The units above describe HealthKit measurement semantics rather than a promised sync format. Database coverage and Apple Health availability are separate questions.
Understanding your records
Recording frequency, source and coverage affect what you can conclude from this data. Read the recording guide.
- One record
- Distance below the water surface; length units, not pressure or a dive safety classification.
- Frequency
- Source-dependent contributions, spot readings or recorded intervals; no empirical cadence was available.
- Context
- Interpret timing and source method for the specific measurement; timestamp overlap does not establish shared session identity.
- Coverage and gaps
- No observations in the reviewed reporting window; database absence is not a zero reading or proof of absence on the phone.
- Summaries
- Discrete values are not cumulative totals. Use compatible units, durations, coverage and source methods for summaries.
- Metadata
- Optional source metadata does not establish complete measurement method or context; no records were available to inspect.
Recording guidance reviewed 2026-10-14