It doesn't depend on whether the seal is a mammal or not. A seal has a thick layer of fat -'<u>blubber</u>' that helps them to stay warm in the cold polar seas. This layer of fat or <u>blubber</u> is not found in humans as we live in warmer areas & hence don't have a need for it. So, humans will die in the cold polar seas without extra protection unlike seals.