The girl is believed to have been stung on the arm while swimming in Nickol Bay.
A WA Country Health spokeswoman said it was the first reported irukandji case in the Pilbara this year.
The Irukandji jellyfish is one of the smallest jellyfish species. On average, its bell, or main section, is less than one inch across! In addition, it is nearly transparent, which makes it extremely difficult to see in the water.
This jellyfish has four tentacles, one attached to each corner of its square-shaped bell. The cubic bell shape is where the box jellyfish group actually gets its name. Interestingly, the Irukandji’s tentacles are retractable, which is unusual.
Like most box jellies, Irukandji live in warm waters. Specifically, they are found off the Northern coast of Australia, along the Great Barrier Reef. Irukandji are found in deeper water, farther from shore than most other box jellyfish species. This is not to say they live in the open ocean. The Great Barrier Reef is enormous and has many deeper sections. Irukandji live in water that is 33 to 66 feet deep. They are occasionally found in shallower water, but only when pushed there by the current or tide.