1) Family: Otariidae which are the seals and sea lions. They in fact are different!
*Sea Lions have flexible hind flippers which they can put underneath them so they can almost "crawl" (or hop on all fours) across a hard surface. They also have ear flaps and normally grow to be much larger than a seal. Here are a couple examples:
..A Northern Sea Lion
..Some Sea Lions at Sea World in Orlando, Florida
..A picture of me and the New England Aquarium's Sea Lion, Guthrie
..Another picture of me and the New England Aquarium's Sea Lion, Guthrie
..And yet another picture of me and the New England Aquarium's Sea Lion, Guthrie

*Seals on the other hand cannot rotate their hind flippers beneath them so they tend to crawl across surfaces on their bellies.
Here is an example:
..A Harbor Seal taken at the New England Aquarium in Boston, Massachusetts.
..Another Harbor Seal taken at the New England Aquarium in Boston, Massachusetts.
..Another picture of Harbor Seals taken at the New England Aquarium in Boston, Massachusetts.
..More Harbor Seals taken at the New England Aquarium in Boston, Massachusetts.
..Another picture of Harbor Seals taken at the New England Aquarium in Boston, Massachusetts.

*Both Seals and Sea Lions eat a variety of marine life, such as Herring and other fish, Squid, etc. They are also highly intelligent mammals and can learn fairly easily how to mimic behaviors and communicate.

2) Family: Odobenidae--Walrus. They live in shallow, cold arctic seas. The walrus has only two other enemies, besides humans, the Killer Whale and the Polar Bear. Walruses usually do not spend too much time at sea; instead, they live most of the time on the ice, hunting for food on the bottom of shallow seas. A female walrus gives birth to one calf every two years. Walruses use their tusks to lift them onto the ice from the water. They also use their tusks to find clams which is their primary food source.

Information provided by: http://www.cyhaus.com