A Deep Sea Jellyfish
While these organisms are classified as marine animals, they don’t have any bones, brains, or blood. Jellyfish vary in size and color. In order to become bioluminescent, some species use green fluorescent protein. Just like fireflies, this type of jellyfish creates its own light, while other species of jellyfish tend to sting anything that crosses their path, and the outcome can be deadly. The most dangerous marine animal in the world is called the Box Jellyfish. It has enough venom in one sting to kill several people, so watch out for that one!