gobiodon

My deepest dive with the Insta 360 One X2 in Insta dive case was 29 m. It worked OK. Company claims it's waterproof until 45 m.

If you have the budget, why not. Big production companies used the predecessor of this camera (Blue Planet).

I feel really sorry. I knew him only from the wetpixel forum, but I really liked his posts and we had some private chat. He was a really nice person. I also very much appreciated his work, since I started diving in the Mediterranean Sea. RIP David.

What about using two parallel gopro, insta360 or similar action cameras (for video)?

It was a fantastic project. I have the book and saw the full movie.

Actually I'm planning to go for Sony A6400. If you're a Sony shooter and not interested in full frame it's a very solid choice. How do you want to use your footage? For YouTube and other social media it's more than enough. I've sold footage for TV production taken by A6000 (not strong in video)

What about "yawning" fish photos. As I know it's also a stress response.

Check this post:

In my opinion, to have a better wide angle camera than GoPro, you have to spend lots of money, and it won't be travel friendly

It was a time ago, but I ordered from this German company and I was satisfied with them: https://www.lichtdekor.de/Lichtfasern/Lichtfasern-Endlicht-170/ I think ordering from other EU contries would also be without problem

I've considered this camera but I didn't find it better than any other top action cameras. It uses a bit outdated sensor and the only advantage is the mechanical stabilization. I agree with you that top action cameras are great and even good enough for TV broadcasting. Sometimes they're better tools than bigger large sensor cameras.

Do you have the proper dome port for this lens?

Nice work Freediver360

Awesome

Very nice. It's time to invest into a VR headset. Which camera(s) have you used?