A slough is a swampy or marshy area.
Sloughs are often wet and muddy, and can be hard to walk through.
Examples:
The ducks swim in the slough.
We saw a lot of frogs in the slough.
The slough is a home for many animals.
I don't like to walk in the slough because it's too muddy.
The slough is so wet, you can't walk through it without getting your feet all muddy.
The slough is a great place for animals to live.