Thanks so much for sharing this! Quite wonderful. I'd love to go back with my 360 camera to get some footage because flat screen video never quite catches the feeling of being in those kinds of spaces.
In this particular case it was a very spacious set of cenotes with a guiding string along the safe route. So it felt pretty safe. It was also the day after we had done some open water diving so the dive master got a feel for our skills (I would assume) and none of us were particularly foolish. I doubt I'd ever want to go diving in actual caves with anything even remotely tight for space.
Diving in the cenotes is pretty damn awesome though! You just have to make sure to dive the ones that have been explored and have designated routes. My third and fourth dives after getting my open water certification were in cenotes around Playa Del Carmen and that experience was just mind blowing. Would love to do it again.
I'm curious what it was about Final Architecture that made you not continue. As I found myself hooked. Just looking to hear an alternate perspective is all.
I'm surprised no one has mentioned Adrian Tchaikovsky yet. I rather enjoyed the Children of Time and The Final Architecture series. They both technically contain bits of Earth but should still fit into the conditions you're after.