Nothing about the hundreds of octopus moms on the video feed from the submersible Alvin looked right.
"Those octopus shouldn't be there," Janet Voight, a marine biologist at the Field Museum in Chicago, said when she saw the footage.
The research vessel was exploring a rocky outcrop about 1.2 miles deep and 150 miles off Costa Rica's Pacific coast—far deeper than any other known octopus nursery, and (in theory) too warm.
"It was jaw-dropping," says Anne Hartwell, a research assistant at the University of Akron in Ohio, who led a new study on the 2014 footage of the octomoms guarding their precious eggs. (See our most beautiful octopus pictures.)
With Voight's help, Hartwell identified the plentiful cephalopods as part