Undersea world

Jellyfish can see.

If you look closely at the edge of the jellyfish's umbrella, you will see small organs called ropalia. They contain the sensory structures of the jellyfish: not only organs that perceive light, but also balance organs, environmental pressure sensors, and chemical receptors. The box jellyfish has four ropalia, each with 6 eyes, for a total of 24 units. Eight of them have fully functional lenses, a retina, and an iris that opens and closes like ours when it gets brighter or darker.