Got real into Subnautica when I made this last year: the bioluminescent aquatic environments and lifeforms..
Tried a different approach with this one. To build up the feeling of depth, light and shadow, I worked in grayscale first, and put a gradient map on it to make it look a little more inviting.
I was an idiot and did this over like a weekend and my hand did a big hurty when I was done. don't be like me kids, take care of your hands