Cavernularia obesa is a sea pen (order Pennatulacea, family Cavernulariidae) found in soft-sediment habitats in shallow to moderately deep waters of the Indo-Pacific, with a primary axial polyp bearing lateral branches colonized by feeding and reproductive zooid polyps. It is bioluminescent, producing flashes of blue-green light when disturbed, possibly serving as a predator deterrent. Sea pens are important members of soft-sediment benthic communities and are particularly sensitive to bottom trawling disturbance. Genomic data have been generated for this species and are available in public databases, enabling comparative studies of cnidarian evolution and ecology.