How to Use Tethys Probe with a COSMIQ+ Dive Computer

Tethys Probe is a read-only Android diagnostic app for COSMIQ and COSMIQ+ dive computers.

It was created to help identify differences between COSMIQ hardware generations and firmware versions. The main Tethys development device is a COSMIQ+ Gen 4 running firmware 1.8, so reports from other devices are especially useful.

Tethys Probe reads available device information, asks a few optional questions about what appears on the COSMIQ screen and creates a text report that you can review before sharing.

It does not change settings, write data to the dive computer or send anything over the internet.

Before you begin

You will need:

  • a COSMIQ or COSMIQ+ dive computer;
  • an Android phone running Android 8.0 or newer;
  • Bluetooth enabled on the phone;
  • the COSMIQ ready to enter Sync Mode.

Tethys Probe is not a dive-planning or safety tool. Use the controls and information on your dive computer for diving decisions.

1. Download Tethys Probe

Download the APK only from the official Tethys Probe release page:

Official Tethys Probe Releases on GitLab

Use the release page rather than an APK copied to an unofficial download site. It always provides the latest public version and its current installation file.

2. Install the APK

Because Tethys Probe is currently distributed outside Google Play, Android may ask you to allow installation from the app used to open the APK.

The exact wording varies by phone. Look for an option such as:

  • Install unknown apps; or
  • Install from unknown sources.

Allow installation for the browser or file manager that opened the APK, then confirm the installation. You can disable that installation permission again afterwards.

Tethys Probe and the full Tethys app are separate applications. Installing Probe does not replace Tethys.

3. Grant the required Bluetooth permission

Tethys Probe asks for Bluetooth access when it starts for the first time.

  • On Android 12 and newer, Android requests Bluetooth permissions.
  • On Android 11 and older, Android requires location permission for Bluetooth scanning.

The location request on older Android versions is an operating-system requirement for discovering nearby Bluetooth devices. Tethys Probe does not request internet permission, so it cannot transmit your location or report automatically.

4. Put the COSMIQ into Sync Mode

Use the MODE button on your COSMIQ to navigate to Sync Mode.

Enter Sync Mode immediately before starting the read. The dive computer leaves this mode automatically after a few minutes. Once it does, it disappears from Bluetooth scanning.

If Probe finds no device, wake the COSMIQ, return it to Sync Mode and try again.

5. Start the diagnostic read

Open Tethys Probe and start the read while the COSMIQ is still in Sync Mode. Keep the phone and dive computer close to each other until the process finishes.

Some COSMIQ generations may not answer every command. This is expected and does not necessarily mean that the diagnostic process failed. A command that receives no answer can itself help identify protocol differences between generations.

Let Probe continue until it completes the process.

6. Answer the optional screen questions

Probe may ask what you can see on the dive-computer screen, including:

  • displayed units;
  • alarm values;
  • the default dive mode;
  • battery bars;
  • other visible device information.

Every answer is optional. There is also a free-text field for information that the app did not ask about.

These answers help compare the raw values read over Bluetooth with the values shown by the device. Complete only the fields you can verify directly.

7. Review the diagnostic report

Tethys Probe creates a plain-text report that can be opened and inspected before it is saved or shared. What you see in the report is what leaves your phone if you choose to send it.

Included in the report

  • answers returned by read commands, represented as raw hexadecimal bytes;
  • model, manufacturer, firmware and hardware revision reported by the device;
  • Android version and phone model;
  • answers you chose to provide about the COSMIQ screen.

Off by default

The following sections are controlled by separate switches because they may contain information about you rather than only the device:

  • Bluetooth address — identifies the particular device;
  • Device clock — may reveal time-zone or routine information;
  • Dive records — may include dive dates, depths and durations;
  • Exchange log — contains raw communication frames from the session.

If a section is switched off, it is absent from the report rather than merely hidden. Review the complete report and enable only the optional sections you are comfortable sharing.

8. Save or send the report

The report remains a file on your phone until you decide what to do with it. Tethys Probe has no internet permission and cannot upload it automatically.

If you would like to help improve COSMIQ compatibility, email the report as an attachment to:

tethys.diveapp@gmail.com

Suggested email subject:

Tethys Probe report

If possible, also include:

  • your COSMIQ or COSMIQ+ generation, if known;
  • firmware version shown in Sync Mode;
  • Tethys Probe version;
  • Android phone model and Android version;
  • whether the read completed successfully;
  • anything unexpected that appeared during the process.

Information from a report will not be published without asking first. Bluetooth addresses and dive locations will not be published.

Troubleshooting

Probe cannot find the COSMIQ

  • Confirm that Bluetooth is enabled on the phone.
  • Confirm that the required Bluetooth or location permission was granted.
  • Wake the COSMIQ and put it back into Sync Mode.
  • Keep the phone close to the dive computer.
  • Close other applications that may already be connected to the COSMIQ.
  • Start the read again before Sync Mode times out.

Some commands receive no answer

This may be a useful diagnostic result rather than an error. Different COSMIQ generations can respond differently. Let Probe finish and mention the result when sending the report.

The process stops or behaves unexpectedly

Try again after returning the COSMIQ to Sync Mode. If the problem continues, send a description of what happened together with the phone model, Android version, COSMIQ firmware and Tethys Probe version.

Why these reports matter

Tethys is currently developed against one physical device: a COSMIQ+ Gen 4 running firmware 1.8. Other generations may use different responses or protocol details.

A Tethys Probe report helps document those differences without writing anything to the dive computer. Reports from real devices are necessary before additional COSMIQ generations can be described as supported.

You can follow confirmed information on the COSMIQ+ Support page and the current implementation state on the Project Status page.

Own a COSMIQ or COSMIQ+?
Run the read-only Tethys Probe, inspect the report and share it only if you are comfortable doing so. Even a successful report from a known device is useful.

Tethys Probe is provided as is, without warranty. It is not a dive-planning or safety tool. Tethys is an independent project and is not affiliated with, endorsed by or supported by Deepblu or the original COSMIQ+ manufacturer.

Last updated: September 2026

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