I recently saw this article on how Greenland Sharks may live for more than 400 years!
The team used these well-dated sharks as starting points for a growth curve that could estimate the ages of the other sharks based on their sizes. To do this, they started with the fact that newborn Greenland sharks are 42 centimeters long. They also relied on a technique researchers have long used to calculate the ages of sediments—say in an archaeological dig—based on both their radiocarbon dates and how far below the surface they happen to be. In this case, researchers
correlated radiocarbon dates with shark length to calculate the age of their sharks. The oldest was 392 plus or minus 120 years, they report today in Science. That makes Greenland sharks the longest lived vertebrates on record by a huge margin; the next oldest is the bowhead whale, at 211 years old. And given the size of most pregnant females—close to 4 meters—they are at least 150 years old before they have young, the group estimates.
Greenland sharks are pretty incredible creatures: they have very high concentrations of urea in their bodies, which is why Icelandic fermented shark (aka "hakarl") has to be fermented before serving.
I didn't try Hakarl when I was in Iceland, but the history around it is fascinating.
Can you even imagine the things Greenland sharks have seen in their lifetimes? Incredible.