Wasp-jelly

Defined as "a small aquatic creature that appears to be made of jelly but stings severely when touched". In the real world, a jellyfish.

Siuan references them when mentioning the danger of stirring up the Asha'man:

Besides, as long the Asha’man stay out of Caemlyn, no one wants to take the chance of stirring them up. The way things stand, we might as well try pulling wasp-jellies out of the water with our bare hands, and even the Greens know it.