I couldn't find reference for the low angle view of the coral and other underwater objects. Flexible thinking was required. I asked myself, what else do I have access to that would have an approximate shape and structure of the things I wanted to draw? Oyster mushrooms!
I lit them in a similar fashion to what I was imagining the light in the picture to be. This gave me enough information to better understand the low angle, and overlapping shelves. Then I had to imagine how the light and objects would work together underwater. It came together the more I worked with the image and pushed the pencil around (butt in chair time).