Below the dish shaped bell of the blue hair jellyfish there are four lobed mouth-tentacles. Around these four tentacles there is a ring of long thin tentacles with poisonous nematocysts. The edge of the bell has eight lobes and there are radial lines running from the edge to a central circle. The nematocysts can inflict a strong pain and burning sensation.

The diameter of the bell is maximum 300 mm. The mouth-tentacles are shorter the other tentacles, that can reach to a length of more than 1 meter.

The tentacles are transparent to murky white, the bell is blue to bluish purple.

In open water.

Shallow coastal waters of the north eastern Atlantic, from Iceland to Spain.