Hi everybody, my name is Jochen

First - my English isn't the best, so I use Google Translator to write. If something sounds "weird", please ask and I'll try something different.

I'm Jochen, I'm 55 years old and I come from Paderborn / Germany. I have been interested in robotics since my apprenticeship as a machinist in 1985 and began my professional life as a setter and service engineer in 1989 for a large machining center group. I worked as a service engineer worldwide for 16 years and am currently working as an assembler in an American company here in Germany.
Hopefully I will retire in about 10 years.

Why am I here in the forum?
I've been working with the Raspberry Pi for a long time, but only as a hobby. Almost 2 years ago (July 24th, 2022), 2 young people drowned while swimming in an quarry pond near Porta Westfalica. It took search teams more than a week to find the bodies. It then took the divers two days to bring the drowned people back to their families.

I would like to ?
I dived in quarry lakes myself years ago as a recreational diver and know how dangerous they are. Currents, shallows, vegetation and also wrecks are very dangerous.
My idea now is to build an autonomous sonar boat that can work 24/7. I would like to relieve the search teams and have my sonar boat work at night, for example.
The sonar boats that I have found so far on YouTube or on the Internet all have the same design - simple hull, maximum of 2 motors, a simple underwater sonar, simple GPS receiver - can I say that the control comes from ArduPilot ?

I don't have a club or company behind me, I'm paying for the development entirely on my own - but I also don't have the time pressure to have the boat launched in the next 14 days.
I just want to build a sonar boat that can help search teams worldwide - side-scan sonar / magnetometer / ready-for-ROV

Greetings to all