What ocean is also considered an official sea

The sea is the interconnected system of all the Earth's oceanic waters, including the Atlantic, Pacific, Indian, Southern and Arctic Oceans. However, the word "sea" can also be used for many specific, much smaller bodies of seawater, such as the North Sea or the Red Sea.

The Arctic Ocean is also considered an official sea.

Explanation:

Many believe that the Arctic Ocean is just another estuary of the bigger Atlantic Ocean. The Arctic Ocean, being the smallest recognized ocean on the planet, is debated to be categorized as a sea. The reasons that are asserted in the support of this argument are that the Arctic Ocean, compared to the other ocean, is not big enough to be called an ocean, and moreover, it is also not as deep as any other oceans in the world.