Tethys Dev Journal #01 — Building the COSMIQ+ Companion App

August 2026


Version: 

  • Tethys 0.10.4.0 (not released yet)
  • Tethys Probe 0.3.1.0 (download)

The leading zero stays until beta.


Deepblu left the market, the COSMIQ+ app is gone from the stores and its servers are switched off —

and the dive computers themselves still work perfectly. Tethys is an Android app that talks to them

again: it reads your dives onto your phone, keeps them there, and changes the settings the device

lets us change safely. This is the first entry in the journal, written from a real COSMIQ+ Gen 4 on

firmware 1.8.


ADDED

  • Bluetooth connection to a COSMIQ+ Gen 4, with the dives downloaded onto the phone
  • A log book where a dive is your record: site, buddies, dive centre, how it felt, notes
  • Export to UDDF, CSV and JSON, so your dives can leave for another app whenever you want
  • Dive site coordinates, marked from GPS before the dive or pasted from a map — all of it offline
  • Gear profiles: a named set of suit, weight and cylinder that fills a dive in one tap
  • Certification cards, and a list that holds more than one dive computer
  • Settings written back to the device — only the ones that are not life-safety, each verified by reading it back afterwards
  • Tethys Probe: a separate read-only app that builds a diagnostic report about your dive computer


TESTING

  • Everything is tested on a COSMIQ+ Gen 4, firmware 1.8, over Bluetooth
  • The protocol was recovered from the old app and verified against that live device
  • Gen 5 and the generations before Gen 4 have never been tested — nobody here owns one


NEXT

  • Making the log book complete enough to replace the notebook
  • More dives read from a real device, including long ones
  • Getting Tethys ready for a public beta
  • Finding owners of other COSMIQ+ generations, so their devices can be supported from real data


Own a COSMIQ+?

Tethys is developed and tested with real COSMIQ+ dive computers. If you own one — especially a

generation other than Gen 4 — Tethys Probe reads your device and builds a diagnostic report you

can inspect in full before sending. It contains no code that writes to your dive computer.


Get in touch: tethys.diveapp@gmail.com


Tethys reads your dive computer; it is not a dive planning or safety tool.

Your dive computer stays your dive computer.


Deepblu and COSMIQ+ are trademarks of their respective owners.

This project is not affiliated with Deepblu.