What happen in autonomous mission when GPS is lost?

Hi, I am new to QGC and to this forum.
Before buying expensive stuff (pixhawk and drones) I would like to know if my idea can be achieve and how the vehicule|QGC|pixhawk would behave in the following situation:
I plan to use the Autonomous Mission feature in QGC. For navigation, the vehicule will have access to a GPS and accelerometer BUT at predefine waypoints, the vehicule would stop and dive (underwater from surface to the bottom and back up). Navigation during the dive would be achieve with a pressure sensor/sonar and would be strictly vertical and GPS signal would be lost.
At the end of the dive, the vehicule come back to the surface and acquire back the GPS signal and continu the autonomous mission until next waypoint (dive point) and return home at the very end.

My concern are: does the vehicule would enter a ‘panic mode’ when GPS is lost? Can we control this aspect? Would the vehicule automatically continu is route as planned upon retrieveing the GPS signal? Since it don’t fly (more like a boat) there is no real danger for the vehicule to fell on someone. Can the vehicule just ‘‘pause’’ the autonomous mission when GPS is lost?

any input will be very much appreciated
thank you

When position lock is lost, vehicle will fall back to the mode which it can achieve with any available position information.

In you case, when GPS lost but your depth sensor is still working, it will fall back to altitude mode, drifting around since no other information available.

You need to change the code if you want other kind of behavior.

Thank you for clear answer.