I just made some dives with my Insta360 and the 1" Leica sensor with the original housing from Insta360. I flooded my first Insta360 because Anti Fog Inserts got between the seal. So be careful with it. The Insta360 without the Lens Cap (you have to take it away for fitting into the hosuing) is not waterproof by itself. Do not expect great support from Insta360. They will ask you to ship your broken Camera to the other side of the world which is very expensive.
I made some dives in Cenotes (bad lighting) and at Cozumel in the ocean (very good visibility and a lot of natural light). I never used any special video lights, just a normal torch in Cenotes.
Video Quality in Cenotes (bad lighting):
The Video Quality was compared to the Panasonic DC-FT7 fabulous! Where the Panasonic Camera just made black videos, the Insta360 was able to catch some great scenes. Sharp Photos were not possible.
Video Quality in Cozumel (very good visibility and a lot of natural light):
The Videos are razorblade sharp BUT everything is blue. Also if I try to activate "AquaVision" in the Insta360-App for exporting the Videos, the colors are just really bad! I've tried to change the color temperature, brightness, etc. with Shotcut and Magix Video Editor but the result was still pretty bad. At Cozumel the sand is really white, in the videos sometimes it looks overlighted because of the sun reflection. I had a Panasonic DC-FT7 with me on the dives. The color quality and at all the video quality was way more better! I will
Regarding your questions:
- I make 5.3k Videos and the battery consumption is pretty ok an will last about for one 50 Minutes dive
- It does not overheat but make sure to use Anti Fog inserts
Let me know, if you want to see some footages.