nudibranch glossodoris atromarginata moving left to right over dark sandy bottom, close-up shot showing all body parts

nudibranch glossodoris dorid atromarginata scuba mollusk gastropod rhinophore reef biodiversity gastropoda underwater chromodoridae aquatic diving ophistobranchia coral sea animal wildlife aeolid biology mucus ecosystem mantle indopacific environment closeup indonesia ocean beauty horizontal wild marine curling nature macro dark margin water tropical white color life colorful black