For time:

Row 1,000 meters
Rest 3 minutes
Row 750 meters
Rest 3 minutes
Row 500 meters
Rest 3 minute
Row 250 meters

Post times to comments.

Scaling:
With rest included, this should not exceed 25 minutes for most athletes. If you are a newer athlete and have the time, complete all of the work focusing on rowing technique, even if you expect it will stretch beyond the 25 minutes.