A female polar bear swam for a record-breaking nine days straight, traversing 426 miles of water!

The data in this study was acquired between 2004 and 2009, when biologists collared 68 female polar bears to observe their movement patterns. The incredible mother bear traveled a length approximately equal to the distance between Boston and Washington, D.C.! The bear also lost 22 percent of its body weight during the nine-day aquatic journey, and tragically, her young cub alo passed away. These sorts of marathon swims are a new phenomenon for polar bears with the shrinking ice caps caused by global warming, and it appears that they will only be getting longer. The data was also compared to cub losses, and the researchers found that mothers who swim long distances are more likely to experience the death of their young.
(source)