Cubozoan jellyfish carry four rhopalia, small sensory structures set into niches around the bell. Each rhopalium bears six eyes: two simple pit eyes, two slit eyes, and two camera-type eyes with a graded-index lens, cornea and retina. Twenty-four in total.
The upper lens eye points reliably towards the sky regardless of how the bell tilts, because each rhopalium hangs on a stalk with a heavy crystal that keeps it oriented by gravity. Experiments on the mangrove-dwelling cubozoan Tripedalia cystophora showed the animals using that upward view to see the mangrove canopy and stay near it, which is navigation by image, not by simple light-dark sensing.
What cubozoans lack is a brain. Processing happens in the rhopalial nervous systems and a nerve ring around the bell margin. The lens eyes are also substantially out of focus, projecting a blurred image, which appears to filter out fine detail and leave large stable features such as trees or pilings. Chironex fleckeri swims actively at speeds of a few kilometres per hour and can avoid obstacles rather than drifting into them.