YouTube
Almost half an hour, because I've got lost for over five minutes trying to figure the way underwater.
By the way, this is a 16:9 480p video, because higher resolutions would stutter when capturing. I've experimented a lot with different settings over the last days, and this is the best video quality I can get with my current computer.
When I get around to buying a computer with a Ryzen Threadripper I'll be able to record higher-res videos (already got the money, but no time for building the thing).