Macro - Nudibranch - Tambja Abdere - Sea of Cortez. Nudibranchs are actually a type of sea slug. They appear in all types of colors and sizes. This one was less than 1 inch long. They are actually very amazing creatures and many underwater photographers focus on shooting Nudibranchs only.
The antenna looking protrusions atop of their head are called rinophores -- which detect taste, touch and smell. The plumage like appendage that appears on the back end are actually their gills that they use to breath with. They are actually quite complex creatures with unique diets, activity and mating habits.