A Diaphanous Killer

The Irukandji is practically invisible in ocean water.

The Irukandji jellyfish is an extremely small but deadly creature. Its flimsy, diaphanous body is as small as your baby finger nail, and it will die upon impact from simply drifting into a flat surface. However, its sting penetrates directly through the skin and causes an excruciatingly painful, if not fatal bout of symptoms.

Diaphanous

1.  Characterized by such fineness of texture as to permit seeing through; diaphanous fabrics
2. *Characterized by extreme delicacy of form : ethereal; painted diaphanous landscapes

Synonyms

gossamer, pellucid, translucent, transparent

Further Reading

Wikipedia: Irukandji Jellyfish