Seaweed
Duckweed, Algae
noun
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.
藻が絡まってしまったみたいだ。
The duckweed seems to be twisted up.