Box jellyfish glide through tropical shallows with an almost delicate grace, yet their venom ranks among the most lethal on ...

Beachgoers should watch for box jellyfish in Guam's waters for three days next week as the marine animals follow their monthly pattern tied to moon phases.

The box jellyfish carries venom powerful enough to stop the human heart within minutes. Medical experts say survival often depends on immediate treatment, as antivenom is not always effective.