Halimeda Ghost Pipefish
Of all the species of Ghost Pipefish, this one takes the prize for mimicry. It's named for a species of green algae called Halimeda. This pipefish is almost a perfect replica of a section of this algae. If this fish was in a bed of Halimeda algae, it would be quite invisible.
Lembeh Strait, North Sulawesi, Indonesia