Which of the following is not a swimming stroke ?

Swimming strokes are specific ways to move through water. The four official strokes are crawl (freestyle), backstroke, breaststroke, and butterfly. Each has its own arm and leg movements.

Downstroke is not a recognized swimming stroke. It might sound similar to real strokes, but it is not taught or used in competitive swimming.

The term downstroke does not exist in swimming terminology. All other options are actual swimming strokes used in competitions and swimming lessons worldwide.