Compared to the generic "jellyfish-shape" most are familiar with, the crystal jelly is flattened and saucer-shaped. It can grow up to 60cm wide.
Its bell is transparent, thin at the edge and thickening towards the central portion. Up to 80 distinct white channels can be seen running from the edge of the bell to this central portion.
The crystal jelly has a multitude of short, fine tentacles. Its oral arms, or manubria, are short and do not extend far beyond the bell.
The crystal jelly often has bioluminescent algae growing on the edge of its bell, and can thus be seen "glowing in the dark." It is able to control this bioluminescence to an extent, and many are able to display alternating flashes of blue and green light.
The crystal jelly is a hydrozoan jelly and has the largest medusa stage of any jellyfish of this type. Although relatively rare, it can occur in huge swarms when conditions are favourable.