Scientists know the Greenland shark (Somniosus microcephalus) moves slowly in the Arctic's cold water. They also know that parasites attack the shark's eyes. But much about this animal remains a mystery. Marine biologist Greg Skomal says that's because the Greenland shark spends most of the year living under 6 feet of Arctic ice. Skomal works for the Massachusetts Division of Marine Fisheries. In this episode of the Encyclopedia of Life's One Species at a Time podcast, Skomal tells reporter Ari Daniel Shapiro what it's like to study these apex predators in the wild.