See-through cephalopod

One of the least understood of sea creatures, this glass octopus lives in the depths of the ocean where sunlight can't reach, about 900 metres down. Glass octopuses are rarely seen and difficult to observe, but they're a great example of the diversity of the order Octopoda, which we're celebrating today on World Octopus Day. The observance comes around, appropriately, every October 8.
© Solvin Zankl/Minden Pictures