Explanation:

- Sargasso Sea:

- This sea is unique as it is defined by ocean currents rather than land boundaries.

- Located in the North Atlantic Ocean, it's encircled by the Gulf Stream, North Atlantic Current, Canary Current, and North Atlantic Equatorial Current.

- Not bordered by land, making it distinct.

- Pechora Sea:

- Lies off the northwest coast of Russia.

- Part of the Barents Sea, and is bordered by the Russian landmass.

- Amundsen Sea:

- Located off the coast of West Antarctica.

- Bordered by the Antarctic landmass.

- Iroise Sea:

- Situated off the coast of Brittany, France.

- Surrounded by land on the north and east sides.

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