In the Pacific Ocean and parts of the Red Sea, bubble coral can be found in varying species, colors and forms. They maintain their egg-like appearance during the sunlit hours (maybe an egg-like disguise?), then deflate at dark, manifesting finger-tentacles that feed on plankton, etc.
See more of this beautiful creature at Environmental Graffiti.
Previously on Neatorama: Great Barrier Reef: Gone in 20 Years