Most jellyfish, while considered slimy, disgusting and just plain annoying, will do little more than inflict a mild sting if an unwary swimmer happens to bump into them by mistake while swimming or wading along the shore line. They are typically not strong enough to resist the current and will become victim to the tide if they are unfortunate enough to get too close to shore. The jellyfish often seen washed up on beaches are of this type.
There is a species of jellyfish however, the largest of which is known scientifically as Chironex Fleckeri of the class Cubozoa, which defies the typical description of the jellyfish. This species of jellyfish, commonly referred to as the box jellyfish or, alternately as the Sea Wasp, Fire Medusa or Stinger, is native to the tropical Australian waters and the Indo-Pacific ocean region. They are exceptional swimmers with enough agility to make their way around obstacles in the ocean and to avoid easy capture; they are rarely found washed up on shore.
The box jellyfish is unique among jellyfish in that they possess an actual eye with a retina, cornea and lens. This specialized physical feature can be directly correlated to their ability to actively hunt their prey rather than wait for circumstance and water current to direct them where they need to go.
The Australian box jellyfish is considered to be the most poisonous sea creature known to man. Its painful sting is often fatal and guaranteed to leave significant scarring in those lucky enough to survive its venom. Its pale blue or transparent color makes it difficult to see until it is too late. It gets its name from its shape, with four distinct sides which give it a cube-like shape. At adulthood they may reach around eight inches along each box side or nearly twelve inches in diameter. Each corner consists of about 15 tentacles which may grow to nearly ten feet in length, each of which contains thousands of stinging cells.
Some box jellyfish appear to choose a mate for its reproductive cycle. For some box jellyfish the male reaches a tentacle into the bell of the female and deposits a sperm packet. For others the female deposits eggs directly into the water to be fertilized. This spawning process occurs once each year, late in the summer season. The fertilized eggs become planulae which soon become tiny polyps, attaching themselves to rocks to continue their development into the spring, at which point they are miniature versions of the adult box jellyfish. They break off from the rock and are ready to begin their lives.
The Australian box jellyfish has one natural enemy, other than man of course. That would be the sea turtle which is unaffected by the venomous sting of the box jellyfish and considers the box jellyfish to be a regular part of its diet. As more and more sea turtle run the risk of extinction due to over-fishing of ocean waters, pollution and other means of destroying their natural habitats, an increase in the population of box jellyfish may be a concern to scientists and ocean swimmers in the future.
