Sea otter have a high metabolism and must eat about 20% of their body weight everyday.

sea otter eating sea urchins: http://www.defenders.org/wildlife/new/seaotters.html

Otters about anything available to them, but their favorite meals are abalone, sea urchins, crabs, sea stars, and squid. To catch their meal, otters dive down into the ocean and us their whiskers and nose to feel vibrations in the water. Otters carry their food to the surface using a flap of skin under the armpit and consume the meal floating on their backs.

sea otter eating a sea star: http://library.thinkquest.org/J0111704/diet/diet.html

Otters use their teeth and claws to eat slippery food, such as squid. Sea otters are the only known mamals, other than primates, to use tools. They use rocks and other things they find to pry open a shell or hammer the shell until they can get to the animal they eat.

sea otter eating a crab: http://library.thinkquest.org/J0111704/diet/diet.html

Sea otters are important for they ecology of their habitat. In the kelp beds where the otter lives, sea urchins also live. Sea urchins eat the kelp and the sea otters eat the sea urchins. The populations of the sea urchin and sea otter are directly related. The sea otter keeps the sea urchin from overgrazing the kelp bed and the kelp bed in return the kelp bed gives the otter a home and safety from predators.