Best to stay inside programming.
What the parent doesn't mention in the water alongside the croc and box jelly is the irukandji which is extremely common and extremly dangerous as well while being as small as a fingernail.
With all those things around, Australia is an amazing place, the moral of the story is ask the locals before you do something you'll regret, they are the ones who knows and if you ask before you will be fine
"The first of these jellyfish, Carukia barnesi, was identified in 1964 by Jack Barnes; to prove it was the cause of Irukandji syndrome, he captured the tiny jellyfish and allowed it to sting him, his nine-year-old son and a robust young lifeguard. They all became seriously ill, but survived".
That's some dedication to science.