Turtle seal

The Turtle Seal is green with a hard shell around its midsection and four flippers that allow it to swim well in cold water. The creature has a long, sleek neck and head and its face is characterized by small black eyes, small ears, and whiskers. Unlike the Turtle Duck, whose legs make it look like a tortoise, the Turtle Seal's flippers are its prominent form of transportation They are social creatures that live in herds. These loud, but lovable creatures are native to the North Pole. They especially enjoy swimming through the ice tunnels underneath the Northern Water Tribe. Their hard shells provide them with some protection from their natural enemy, the polar leopard. The turtle seals are carnivorous, eating fish, shellfish, squid, and other ocean creatures.

Turtle Seals first appear in "The Siege of the North, Part 1."

Connection
The Turtle Seal is simply a seal with a turtle's shell, meaning it is connected to the seal and the turtle.