Box jellyfishCubozoa

It can see you. A box jellyfish carries twenty-four eyes, in four clusters spaced around the bell, and two eyes in every cluster are not light-sensitive patches but proper eyes with a cornea, a lens and a retina, built on the same plan as your own. There is no brain behind them. Whatever those eyes resolve goes into a ring of nerve tissue and comes back out as steering.

Each cluster hangs off a short stalk with a weight at the bottom, so it swings like a plumb line. However the animal rolls or tilts, one lens eye in each set stays pointing straight up through the surface. A species in the mangroves of the Caribbean uses that upward view to hold its position under the canopy it feeds in, navigating by the shape of the trees above the water. This is a jellyfish reading the world in air.

The rest of the body is built to act on what the eyes deliver. The bell is square, with a bundle of tentacles trailing from each of the four bottom corners and a muscular rim that turns each pulse into a jet, so the animal swims a course instead of drifting one. Box jellyfish hunt prey that can see them coming, mostly small fish and shrimp, and they will turn away from an obstacle rather than blunder into it.

The question people arrive with is whether these are the ones that kill, and the honest answer is that the killers are not here. The Australian box jellyfish and the small Irukandji species responsible for deaths live in the Indo-Pacific from northern 🇦🇺 Australia, and neither is recorded in the 🌊 Red Sea. What is recorded here is a smaller animal, seldom met in daylight, more likely near lights after dark, and its sting is savage out of proportion to the mark it leaves: burning that starts at once, and raised welts that can last weeks and scar.

That is why the boats carry vinegar. Flooding the skin with it stops the cells still sitting on you from firing, while rubbing the area or rinsing it with fresh water sets them off instead. Lift any tentacle off, keep the vinegar going, and treat anything beyond skin pain as a matter for a hospital rather than for the boat.