Fitness traits of a seal?

Seals are a collective name for two families of animals that had separate ancestors. There are eared seals in the world, which most likely descended from bears, and there are real seals, which, according to scientists, descended from weasels. In both cases, the aquatic lifestyle strongly influenced the appearance of the animals. None / very small ears, streamlined body, small round head to reduce drag. The legs of the animals turned into flippers and were overgrown with a thick membrane between the toes.