Named for their plump, pink, and rounded bodies, sea pigs are very abundant, but you are unlikely to ever see one, living as they do at depths of over 1,200 to 5,000 metres (that’s over three miles!).

(CNN) — Ancient glass sponges. A Barbie-pink sea pig sauntering along the seafloor. A transparent unicumber hovering in the depths. These wonders are just an initial snapshot of fantastic creatures ...