The Sargasso Sea is located in its entirety within the Atlantic Ocean with no surrounding borders. It is placed here on the map because though not in the West Indies, the Sargasso sea is in the area between North America, Azores, and West Indies. The Sargasso Sea is the only sea that does not border any land and is surrounded by only four sea currents. According to Rachel L. Carson, the sea is "roughly as large as the United States" (Carson 117). Carson describes the sea as "a place forgotten by the winds, undisturbed by the strong flow of waters... its waters warm and heavy with salt" (117). The sea is home to the Sargasso sea slug, sargassum fish Pterophryne, and seaweed. It peaks interests from many sailors, researchers, and more due to its haunting tales and ever-growing mystery. The Sargasso Sea is the name of the novel by Jean Rhys that focuses on Antoinette (Bertha Mason) and Mr. Rochester prior to/during the revelation of Jane Eyre.

Rhys, Jean. Wide Sargasso Sea, W. W Norton & Company, 1966.
An interesting article on the sea:
https://www.britannica.com/place/Sargasso-Sea