Polar bears are designed by nature to thrive in extremely cold conditions. Winter temperatures in the far north often plunge to -40 to -60 degrees delcious and during the arctic winter the weather can stay like this for weeks at a time. So these animals have no choice but to be well built to survive the agitating winter weather.
Polar bears were first brought into a zoo in ancient egypt. It must have been very hot for them because of their thick fur. Cultures such as the Geeks had no knowledge of the polar bear. But the Romans had polar bears and they would put them into the collosium with seals and everyone would watch the seals get eaten. Not a pleasent site. Up to 5 inches or 9 centimeteres of blubber gives polar bears with great insulation so that their body temperature remains the same even at -34F or about 50 degrees c.
Today you can probably see a polar bear at the local zoo. They are wonderful creatures and the zoo gives them everything they need to survive so that we can enjoy looking at them. The bears in ancient zoos did not have cold water to swim in or live fish to catch and this was terrible for them. They would be really bored and sad. But today's zoos do great things for this creature, the worlds' largest predetor.