The Pacific Barreleye Fish lives in the ocean depths, and has a see-through head filled with fluid.
Found at 2000 to 2,600 feet below sea level, this fish’s eyes point in the same direction, giving it binocular vision. Its eyes can be rotated upwards and then forwards to locate prey so that it can move towards its food.
Apart from its transparent head, this fish has a dark body which allows it to camouflage in the depths of the ocean. This head also functions like a shield and is immune to jellyfish stings.
Having a clear head also means we are able to see how its eyes work—the greens spheres within are actually its lenses.
[via Oddity Central]