Flatworms are relatively common on coral reefs. Their undulating bodies are perfectly adapted to crawling around this complex habitat, but also for swimming. I found this individual swimming several metres above a sandy bottom in deep water. I used the negative space to highlight the beautiful animal.
Nikon D800, Nikkor 105mm, 1/125, f/18, ISO 100, 2 x Inon Z240 underwater strobes, Subal underwater housing