The depths of the ocean are festooned with the most nightmarish creatures imaginable. You might think you're safe, because these critters live thousands of metres down in a cold dark abyss, but the vampire squid, which looks like a nightmare umbrella, and the frilled shark -- a literal living fossil -- will live on in the recesses of your mind long after you've clicked away. Enjoy these deep sea horrors and try to have a relaxing day afterwards.