A white octopus sat on the seabed, gently waggling its short, stubby arms and peering with beady eyes into the camera of a deep-diving robot.
It was 2016, in waters off Hawaii, at a depth of 4,290 metres (2.6 miles). No one had ever seen an octopus like it, and certainly not so deep. Based on its ghostly appearance, it was nicknamed Casper.
