At first Ha saw nothing, as the submersible’s cameras sought to adjust their aperture and the screen paled. Then—here the “floor” had been cleared. A rough circle of stones marked off a central space, in which walked half a dozen or so crabs. Three of them were missing claws.

This hold had originally been used to transport metal piping, and pipes lay in what at first appeared to be a disordered jumble against a tilted bulkhead. But Ha could see, as the submersible panned, that the jumble had been reordered, with the ends of the pipes aligned in a complicated pattern, their different diameters ordered in a staggered stack that accommodated itself to the space but left each pipe-end with a sort of “shelf” below it created by the pipe underneath. Where there was no “shelf” the pipes were filled with debris, so that only one end was open.

The crabs wandered dully in the cleared space. As in the first, larger hold, there was no movement apparent here, besides the crabs. Then a shape jetted out of the end of one of the pipes—a bolide the size of a human fist. The juvenile octopus extended its mantle and floated, rotating down toward the crabs. Angling in, it flipped one of them over, then another, then a third, before jetting back to its pipe.

A few seconds later another juvenile octopus surged from a pipe-end, righted the three crabs that were attempting to turn themselves back over, flipped another three over, and likewise shot back to its pipe.

This activity repeated itself several times, with the number of crabs being turned over changing with each iteration—three, and then two, and then five, and then one, and then four—always a matching number flipped over by the second octopus, until they seemed to grow bored of it. A last octopus climbed from its tube, floated above the crabs, but returned to its den without touching them.

“A game,” said Dr. Mínervudóttir-Chan.

“Yes,” Ha said. “This appears to be a nursery, here. It makes sense. It is deeper in the ship, where its entrance can be guarded by the adults in the outside chamber. Is there a way in farther?”

“Hatch here sealed.” Altantsetseg was still wearing the battered old translator she had switched back to. “No way farther in ship.”

“Then let’s move back out, and find another way in,” Dr. Mínervudóttir-Chan said. “See what else we can see.”

“Maybe we can return to the hatch where we took our first footage. We saw a mixed group there. At least one adult, many juveniles, and an older octopus that had begun to lose its skin pigmentation,” Evrim said. “Before the uncloaked submersible was destroyed. Maybe we’ll have better luck this time.”

“That space is too dark for this submersible to make much out. We were using a light in there,” Ha said.