On a spring morning in 2009, Mathew Lawrence dropped the anchor of his small boat at a random spot in the middle of a blue ocean bay on the east coast of Australia, and jumped over the side. He swam down on scuba to where the anchor lay, picked it up, and waited. The breeze on the surface nudged the boat, which started to drift, and Matt, holding the anchor, followed.
This bay is well-known for diving, but divers usually visit only a couple of spectacular locations. As the bay is large and typically pretty calm, Matt, a scuba enthusiast who lives nearby, had begun a program of underwater exploration, letting the breeze carry the empty boat around above him until his air ran out and he swam back up to the anchor line. On one of these dives, roaming over a flat sandy area scattered with scallops, he came across something unusual. A pile of empty scallop shells - thousands of them - was roughly centered around what looked like a single rock. On the shell bed were about a dozen octopuses, each in a shallow, excavated den. Matt came down and hovered beside them. The octopuses each had a body about the size of a football, or smaller. They sat with their arms tucked away. They were mostly brown-gray, but their colors changed moment by moment. Their eyes were large, and not too dissimilar to human eyes, except for the dark horizontal pupils - like a cats' eyes turned on their side.
The octopuses watched Mat, and also watched one another. Some started roaming around. They'd haul themselves out of their dens and move over the shell bed in an ambling shuffle. Sometimes it elicited no response from others, but occasionally a pair would dissolve into a multi-armed wrestle. The octopuses seemed to be neither friends nor enemies, but existed in a complicated coexistence. As if the scene were not sufficiently strange, many baby sharks, each just six inches or so long, lay quietly on the shells as the octopus roamed around them.
A couple of years before this I was snorkeling in another bay, in Sydney. This site is full of boulders and reefs. I saw something move under a ledge - something surprisingly large - and went to look down at it. What I found looked like an octopus attached to a turtle. It had a flat body, a prominent head, and eight arms coming straight from the head. The arms were flexible, with suckers - roughly like octopus arms. Its back was fringed with something that looked like a skirt, a few inches wide and moving gently. The animal seemed to be every color at once - red, gray, blue-green. Patterns came and went in a fraction of a second. Amid the patches of color were veins of silver like glowing power lines. The animal hovered a few inches above the sea floor, and then came forward to look at me. As I had expected from the surface, this creature was big - about three feet long. The arms roved and wandered, the colors came and went, and the animal moved forward and back.
This animal was a giant cuttlefish. Cuttlefish are relatives of octopuses, but more closely related to squid. Those three - octopuses, cuttlefish, squid - are all members of a group called the cephalopods. The other well-known cephalopods are nautiluses, deep-sea Pacific shellfish which live quite differently from octopuses and their cousins. Octopuses, cuttlefish and squid have something else in common: their large and complex nervous systems.
