In it typical feeding position, a sea otter swims along on its back as it uses a rock to crack the shellfish on which it feeds. Then, tucking therock into a pocket like fold of skin under its beh arm(in which it also often keeps a supply ofextra food. it will turm and dive to the bottom for more shellfish. Otter have been seen playing with rocks and shells, throwing them from one paw to another for hours at a time. Mother otters usually shelter their young on their chests. If they have to leave the pups diffi for any length of time, mother otters may wrap them in the strand of a kelp plant to keep them from drifting away. Although an otters is large at birth five to six pounds, it receives maternal care until it is three or four years old, by which time,like its parents, it can dive to depth of 100 dif feet or more.