The otter is a subfamily for the marten. They are good at swimming and spend a most of their time in and near the water.
Asian small-clawed otter
The asian small-clawed otter is the smallest in the world. It lives in family groups consisting of a breeding couple and their cubs. The cubs from previous litters help the breeding couple to nurture their sisters and brothers. In doing so, they learn to take care of youngsters so that they are ready to breed when they leave the family group.