The duckweed seems to be twisted up.
The kanji and the word are exactly the same. That means they share meanings as well.
Since this word is made up of a single kanji, it probably uses the kun'yomi reading. You did not learn this reading, so here's a mnemonic to help you:
Swim into a floating group of seaweed and shivers will go up your spine. It feels so gross and slimy that you can't help but moan (も) out in distress.