Blubber is a thick, dense layer of connective tissue and fat tissue, present on walruses, whales and seals. This adipose tissue has a relatively low thermal conductivity (lower than muscle or skin).
The blubber of Arctic marine mammals both stores energy and provides insulation, allowing them to survive in cold water. The thickness of this layer may reach up to 30 cm.
To Arctic indigenous people blubber (especially whale blubber) provided both high energy food and oil for fuel.