Privacy Policy for Wassertemperatur (watchOS and iOS)

Last updated: August 3, 2026

1. Introduction

Wassertemperatur helps you log your dives, swims, and dips with temperature, depth, and duration. This privacy policy explains what data is processed, how it is stored, and what role Apple services play. Wassertemperatur is designed to collect as little personal data as possible: there are no servers of my own, no accounts, no tracking, and no advertising.

2. Data collection and processing

a) Dive measurement data: When you enter the water, the app uses your Apple Watch's depth and temperature sensor to measure water temperature, dive depth, and duration. These values are saved as a dive in your logbook. The legal basis is Article 6(1)(b) GDPR, because this is precisely the function you installed the app for.

For each dive you can also write a free-text note and adjust the name of the body of water yourself. What you enter there is up to you; the note is stored, synchronised and included in the CSV export just like the measurements.

b) Location and weather data (optional): If you have granted location permission, the app requests your location around a dive in order to load the weather and the name of the body of water. This happens when you enter the water and after you surface; a location fix up to two hours old is reused rather than measured again.

Coordinates and the name of the body of water are permanently saved to your logbook only if you enable “Save Location” in Settings (default: off).

Independently of that, the location may reside on your Apple Watch temporarily: if the weather request fails, for instance because you are swimming out of network coverage, the Watch remembers the dive's coordinates in order to add the weather and place name later. The app retries whenever it becomes active, for up to ten days; after that the coordinates are discarded. On iPhone, the app retries the lookup for up to thirty days — but there it only uses coordinates that are saved to your logbook via “Save Location.” If you have “Save Location” switched off, the iPhone holds no coordinates.

The legal basis for processing location data is your consent in the form of the location permission (Article 6(1)(a) GDPR). You can revoke it at any time in your system settings; the app remains usable without weather and place information.

c) Health data (optional): If you enable Apple Health import, the app reads the water temperature values stored there. These are usually the values from your swim workouts; however, all water temperature entries in Apple Health are read, including ones written by other apps. If you enable Apple Health export, the app writes your saved dives to Apple Health as water temperature entries. The app neither reads nor writes any other health data.

Processing takes place exclusively on your device; I do not receive this data and have no access to it. Health data belongs to the special categories of personal data (Article 9(1) GDPR). Both directions are off by default and only become active after you have granted them in the iOS permission dialog. To the extent that this permission constitutes consent within the meaning of Article 9(2)(a) GDPR, the processing is based on that consent; you can withdraw it at any time in your iOS settings or in Apple Health.

d) CSV export and share graphics: You can optionally export your dives as a CSV file or share individual measurements as a graphic. These files are only created and shared when you trigger this yourself via the share function.

e) Feedback by email: If you contact me via “Send an idea,” your mail app transmits your message, including technical details (app version, iOS version, device model), to joe@waldow.app. The legal basis is my legitimate interest in answering your enquiry (Article 6(1)(f) GDPR).

3. Data storage and synchronization

Local storage: Dive measurement data is first stored locally on your Apple Watch and transferred directly to your paired iPhone via Apple WatchConnectivity.

iCloud backup (iOS only): On iPhone, the app additionally syncs your dives to your private iCloud database (CloudKit), so they are preserved if you switch devices or reinstall the app. This data is only accessible with your Apple ID and cannot be viewed by me or by Apple. The Apple Watch itself does not use iCloud backup; it intentionally stays local.

4. Location and weather data (Apple WeatherKit)

Weather data (outside temperature, conditions) comes from Apple WeatherKit. Your location is transmitted to Apple for this purpose.

For the name of the body of water, your location is additionally sent to Apple's geocoding service, which turns it into a place name. The name is therefore not derived on your device.

When you open a map in the logbook or the statistics view, Apple Maps loads the map tiles for your saved dive locations from Apple. Apple thereby learns which area you are looking at.

The recipient of this data is Apple Inc., One Apple Park Way, Cupertino, California, USA, or for users in the EEA Apple Distribution International Ltd., Cork, Ireland. A transfer to the USA may take place; according to Apple, such transfers are based on the European Commission's Standard Contractual Clauses and the EU-US Data Privacy Framework. Apple's Privacy Policy applies, as does Apple Weather's legal attribution. You can revoke location permission at any time in your system settings.

5. No advertising, no tracking, no third-party analytics

Wassertemperatur uses no advertising SDKs, no third-party analytics or tracking services, and no advertising IDs. Your measurement data is never sold or used for advertising purposes.

6. Data deletion and user control

You can delete individual dives in the app at any time, on the Watch or on the iPhone. Deletion is propagated to the other device. Deleting the app removes all local data; the iCloud backup is also removed once it is deleted from the last device. For Health data, you can adjust permissions at any time in iOS Settings or in the Apple Health app; the app can only delete entries it created itself.

Retention: Your dives remain stored until you delete them or remove the app. There is no retention period for them, because the data is yours and I do not hold it. Coordinates cached only on the Apple Watch for the deferred weather lookup are discarded after ten days at the latest. Emails you send me are kept for as long as I need them to deal with your enquiry.

7. Your rights

You have the rights to access, rectification, erasure, restriction of processing, data portability, and objection (Art. 15 to 21 GDPR). Since Wassertemperatur does not transmit data to me, I generally hold no personal data about you, except for emails you send yourself. For data processed through Apple services such as iCloud, HealthKit, or WeatherKit, please refer to your device settings or to Apple.

You also have the right to lodge a complaint with a data protection supervisory authority, in particular in the country of your residence, your place of work or the place of the suspected infringement. For me as the controller, based in Schleswig-Holstein, Germany, the competent authority is:

Unabhängiges Landeszentrum für Datenschutz Schleswig-Holstein (ULD)
Holstenstraße 98
24103 Kiel, Germany
www.datenschutzzentrum.de

No automated decision-making including profiling within the meaning of Art. 22 GDPR takes place.

8. Changes to this privacy policy

This privacy policy may be updated from time to time. The version published on this page at any given time governs.

9. Controller

Wassertemperatur is developed and maintained by:

Joe Waldow
Hasenbusch 52
25335 Elmshorn
Germany
Contact: joe@waldow.app