Some others are:
The Common Seal which is found in Northern Oceans.
It was hunted for its soft-under fur which provided seal skin.
The Inuit (Eskimos) used seals a lot for skins, food and oil
for heating and lighting.
The Sea Otter of the Northern Pacific Ocean has
flipper-like feet a bit like those of a seal. It feeds on shell-fish
and sea-urchins and has been hunted for its fur.
The Northern Sea Bear is smaller than the sea lion
and has larger ears. It has been hunted for its under-fur.
The Sea Elephant of the Pacific Ocean is a mountainous
species of seal. It is a slow mover and has a trunk that seems
to be able to get bigger by swelling up.
The Grampus or Killer is a huge glossy-black member
of the dolphin family. It is a fierce attacker of its prey -
mainly fish, seal and porpoises and is very greedy. It is found
in the Arctic and Antarctic Oceans.
The Narwhal is a type of whale and is found in
the Arctic. It is interesting because it has a straight, spirally-twisted
The Porpoise is found in the North Atlantic and
North Pacific. It travels in a shoal and lives only on fish.
The Dugong or Sea Cow is a gentle, inoffensive
aquatic mammal. It has thick lips and a short snout which help
it browse the vegetation of the tropical seas.
The Manatee is also known as a Sea Cow.
The Polar Bear could also be included if you want
to put a mammal closely associated with the sea.