When we think of animals with long life spans, tortoises usually come to mind first. But even Jonathan, a roughly 189-year-old giant tortoise who resides in St. Helena, would seem positively young compared to the average Greenland shark. Somniosus microcephalus (“sleepy small-head”) can live as long as 400 years or more, meaning there are probably some of them swimming the depths right now who predate the United States — or Sir Isaac Newton, for that matter. The deep-sea dwellers, most commonly found in the Arctic Ocean and North Atlantic, are the world’s longest-living vertebrates.
In addition to their longevity, they’re also quite, well, long: Greenland sharks can reach a length of 23 feet and weigh over 2,000 pounds, though the average specimen isn’t quite that imposing. Despite also being among the world's slowest sharks — they’ve been observed “almost immobile” while “practically hovering” above the sea floor — they’re capable of quick bursts of speed that allow them to target fast-moving seals, Greenland halibut, Atlantic cod, and other marine creatures. As for how and why Greenland sharks live so long, it’s partially explained by their preferred environs: Cold-blooded animals in cold environments tend to have slow metabolic rates, which are associated with longevity (although scientists are still teasing out why) and “deep and cold equals old.”
The flesh of Greenland sharks contains an unusually high concentration of urea and the compound trimethylamine oxide (TMAO), which protect against cold temperatures and high water pressure. Should one choose to dine on Greenland shark meat that hasn't been dried or soaked, one will experience an intoxicating effect that's been referred to as both “shark sick” and “shark drunk.” That hasn’t stopped it from becoming an Icelandic delicacy, however.
Hákarl is Greenland shark that has been fermented and hung to dry for as long as five months, resulting in a pungent, ammonia-like smell and cheesy texture. Though beloved by some (though certainly not all) Icelanders, it was described by Anthony Bourdain as “the single worst, most disgusting and terrible-tasting thing” he ever ate.