Polar bears are covered with white fur. Their fur does not change color like a chameleon's skin; however, since they live in a snowy zone they are always surrounded by the color white. They do not need to adapt to different color backgrounds like a chameleon does.
Hiding in Water
Although polar bears do not generally like to swim, they will wade into the water to hunt seal if they are looking for food. Often they will put their paw over their nose and mouth so they won't be seen by the seal.
Not all white
A polar bear's outer layer is made up of white fur, in order to hide them better in the snow. Under their fur, however, they have black skin and a layer of fat. This helps keep them warm in the cold Arctic snow. So, between their skin and fat to insulate their bodies and their white fur to camouflage them, polar bears are well suited to their environment.