Apple Watch Ultra: Does an underwater compass app require the full Submerged Depth and Pressure entitlement to operate below 6 meters?

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Hi there,

I'm planning to develop a simple underwater compass app for Apple Watch Ultra 2, intended for recreational scuba diving down to 40 meters.

The app itself does not need depth or pressure measurements beyond 6 meters. Its primary function is compass navigation using heading data.

During a dive, however, I would like the app to:

remain frontmost and visible throughout the dive;
use Water Lock;
use an underwater-depth WKExtendedRuntimeSession;
continue receiving compass heading updates;
allow interaction through physical controls such as the Digital Crown and Action Button;
remain operational below 6 meters, potentially down to 40 meters.

I understand that the Shallow Depth and Pressure capability limits CMWaterSubmersionManager depth/pressure data to approximately 6 meters, while access to depth/pressure data down to 40 meters requires the full Submerged Depth and Pressure entitlement.

My question is:

If my app does not require depth/pressure measurements beyond 6 meters, is the full Submerged Depth and Pressure entitlement still required simply to keep the underwater extended runtime session, UI, compass heading updates, and physical-control interaction working below 6 meters?

In other words, does the 6-meter entitlement limit apply only to depth/pressure data, or does it also limit the ability of an underwater compass app to remain operational during a scuba dive below 6 meters?

Target hardware: Apple Watch Ultra 2.

Thanks in advance!

Answer 1

DTS Engineer OP

Apple

1h

First off, as a disclaimer, this is the kind of behavior you really to do your own testing to understand and verify. I've answered below based on my own understanding and analysis of CoreLocation and watchOS, however, the system is big and complicated enough that it's entirely possible I've overlooked something.

In any case:

If my app does not require depth/pressure measurements beyond 6 meters, is the full Submerged Depth and Pressure entitlement still required simply to keep the underwater extended runtime session, UI, compass heading updates, and physical-control interaction working below 6 meters?

Yes and no. In terms of "direct" impact, there doesn't seem to be any difference between the two entitlements and I'd expect the system to basically work "the same" with either entitlement.

HOWEVER, what "Submerged" does change is that it shifts the devices definition of "Max Depth" from 6m to 40m. The issue here is that the device is going to start warning you when you cross that threshold and I'm not sure[1] how disruptive that will be to the user.

[1] Diving and owning an Apple Watch Ultra are both pleasures I've been unable to indulge.

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Kevin Elliott
DTS Engineering, CoreOS/Hardware