Multicolored Nudibranch Photograph by Mohammed Alsaleh, My Shot Generally oblong in shape, nudibranchs can be thick or flattened, long or short, ornately colored or drab to match their surroundings. Some max out at a quarter of an inch millimeters)
Nudibranch/Sea Slug ("Cratena peregrina | jordi benitez.") Google search: "Cratena peregrina, commonly called the "pilgrim hervia", is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Facelinidae. Wikipedia."