Box jellyfish  are the most poisonous marine animals known to man. They measure 3 meters long and weigh up to 2 kilograms. They are pale blue and transparent in color, and get their name from the cube--like shape of their body, Box jellyfish have 6 eyes on all 4 sides of their body, although it is uncertain how they process what they see as they do not have a central nervous system. They also have up to 15 tentacles  growing from each corner of their body that have about 5,000 stinging cells each. Box jellyfish can be found primarily in the coastal waters off Northern Australia as well as throughout the Indo--Pacific. They prefer to live at river mouths. They do not have any organs to breathe, and will sleep on the ocean floor from 3 pm to dawn. Unlike other jellyfish that merely move along with the current, box jellyfish have developed a way to travel wherever they want to go. _ will shoot themselves in a jet-like fashion, reaching speeds of up to 7.4 kilometers per hour. The diet of box jellyfish consists of thing like fish, small animals, and even other jellyfish. They use their venom, a chemical which causes heart, skin, and breath failure, to kill their prey . Since box jellyfish have eyes, some scientists believe that they actively hunt their prey while others insist that they are just passive opportunists that will wait and catch anything that wanders into their tentacles. Box jellyfish are responsible for more human deaths in Australia than snakes, sharks, and salt-water crocodiles combined. It is best to avoid them as most stings  will result in death. Hopefully, humans and box jellyfish can find a way to live with one another while keeping conflicts to a bare minimum. After all, such a unique species of jellyfish deserves to live and grow just as humans do. The text is mainly about   _  .
a kind of sea animal some poisonous animals scientists' research into box jellyfish the relationship between humans and jellyfish