Scientists have been amazed by a new discovery about polar bears.
Experts tracking the bears north of Alaska say they now have evidence of the huge distances they can swim without stopping.
In one case they found a bear had travelled a whopping NINE days non stop - that's like swimming from London to Paris and more!
The researchers claim because sea ice there is melting, polar bears are having to swim for longer distances.
By doing this they could be risking their own health and future generations.
Back in November, polar bears were snapped carrying their young on their back as they swam. It's thought it was the first time scientists had seen this.
At the time Geoff York, from charity WWF, said: "As the Arctic ice continues to melt, it is likely that polar bears are going to have to swim longer distances.
"Data from tagged bears near Alaska has indicated swims of 350-400 miles in the past four years."