So I half-heartedly went googling for others who had perhaps tried to make ocean props, maybe for theater, or something random. After some searching, found this lovely website. Looks like they were making coral for decorative purposes, but had some rather genius ideas about making coral look like coral: fake plants! Can't believe I didn't think of it--dur. Grouped together, a bunch of blossoms would definitely look like the coral reefs. I liked several of the arrangements they made.
The coat of texture spray would be a really good way to strip away the flowers to the basic forms. I would then want to paint or spray paint neon colors so that they could be picked up by the blacklights.