The Rose Bubble Shell (Hydatina physis) is a very pretty opisthobranch species that belongs to the family Hydatinidae. This species has been found in the waters of the Red Sea, Africa, Maldives, Philippines, Hawaii, Japan, New Zealand and along the east and west coasts of Australia. This animal has a large body, which it cannot retract fully into its shell. The body is coloured red or pink with a fluorescent blue line around its edge; these colours are very bright and make the species easy to observe. During the daytime this species remains buried in the sand or hiding under rocks and emerges at night to feed on polychaete worms from the family Cirratulidae.
This species can generally be found crawling over sandy or silty bottoms and is known to lay an egg mass that is attached to the sand by a mucous thread. The Rose Bubble Shell (Hydatina physis) grows to a maximum length of approximately 8cm.