Sentence:  Few storms trouble a <WSD>sargasso</WSD> region, and rain rarely falls there even during the spring seasons. These conditions help create massive beds of floating vegetation, dominated by kelps and a weed called sargassum. [...] Of all the regions of the open sea, <WSD>sargassos</WSD> are the ones with the highest biological density, and potentially the most dangerous. 
Meaning of the word marked with <WSD> tags:  A part of an ocean or sea characterized by floating masses of sargassos, like the Sargasso Sea.