Hi @hugokopter -
A DIY glider sounds like a cool project! Unfortunately, you’re ahead of the curve - no autopilot firmware that I’m aware of supports your application. Some significant development may be required! Some groups have had success with using the Navigator WebAssistant to develop swarm AUV controls using our existing Raspberry Pi 4 + Navigator.
I would also point out that your underwater vehicle won’t have GPS link, or the ability to talk to satellites, unless it is at the surface of the water!
Best of luck!