Yodogawa
proper noun
The eddy river isn't so much a thing as it is a famous place. We're talking about Yodogawa. It might be better to look at the reading to learn the meaning. Look up this Osaka Prefecture river if you'd like more info.
The reading is 淀 plus 川. Be careful of the rendaku.
汚い水にも怯まず、彼女は淀川で泳いだ。
The dirty water didn’t stop her swimming in the Yodogawa.