Background Information: Marine mammals are mammals that spend their lives living in the water. Some examples include whales, dolphins, seals, walruses, and manatees. Most marine mammals have smooth rubbery skin that helps them to slip easily through the water. In order to keep warm, their body has a layer of blubber. Blubber is the think layer of fat that the animals use to conserve body heat. Blubber can be six to twenty inches thick. If a mammal's food source is scarce (hard to find), it can live off of its blubber for a long time. Blubber is lighter than water, so it increases buoyancy in marine mammals and helps them to float. Hunters often kill marine mammals such as whales and seals and they heat their blubber to make oil.