The sentence you wrote is mostly clear but can be improved a little to make it smooth and correct. Here's the original sentence:
"Like many water birds, Mandarin ducks have webbed feet. These special feet work like natural flippers helping ducks swim fast and dive underwater, where they can catch fish."
Here is a corrected version with some small changes:
"Like many water birds, Mandarin ducks have webbed feet. These special feet work like natural flippers, helping the ducks swim fast and dive underwater, where they can catch fish."
Explanation of changes:
- I added a comma after "flippers" because the phrase "helping the ducks swim fast and dive underwater" is an extra detail explaining what the flippers do.
- I added "the" before "ducks" because we are talking about the Mandarin ducks mentioned before, so we specify which ducks.
The sentence is now grammatically clear and easy for an 8-year-old to understand!