What gives the Sargasso Sea its unique name?

The Sargasso Sea is named after the large amounts of floating seaweed known as sargassum, which is a type of brown algae. The presence of this seaweed contributes to the unique features of the Sargasso Sea, distinguishing it from other parts of the Atlantic Ocean. The sargassum creates a distinct habitat that supports a variety of marine life, and its dense mats can be an important part of the ecosystem.

The other choices are not applicable as the sea's name specifically derives from the seaweed rather than fish, historical events, or navigational hazards.