Cephalopods

Common Reef (Day) Octopus

Octopus cyanea · Cephalopod mollusk — family Octopodidae; the big day-active octopus of Indo-Pacific reefs, called he'e in Hawaii

This is the octopus most tropical divers actually meet, because it breaks the family rule and hunts by day. A big day octopus flows across the reef as a self-editing special effect — skin texture spiking into algae tufts, color rippling from mottled brown to bone white in under a second, a passing-wave pattern flickering as it moves. Watch a hunt: the animal balloons its web over a coral head and flushes whatever bolts, while jacks or a grouper often shadow it to pick off escapees, one of the reef's neatest hunting partnerships. Dens are readable by the midden of emptied crab shells at the door. Sit still three meters out and curiosity frequently wins, an arm tip arriving to inspect a strobe arm. Let it explore; snatching gear back teaches the animal that divers end hunts.