6. Glaucus Atlanticus
Its size makes him hard to be seen, so it can easily hide from enemies – this tiny gastropod mollusk can be up to 1.2 in length, depending on its age. It’s not just its look that’s so strange, but also its behavior. This almost fantastic animal floats upside down at the surface of the sea.
You can find one of these beautiful creatures throughout the tropical Atlantic, Pacific and Indians oceans. However, it’s strongly recommended not to take it as a pet, because the creature feeds on hydrozoans, especially the Portuguese Man-O’-War which is considered to be extremely poisonous and harmful for humans. Then it can store the poison and use it against enemies when in danger.