Rowing is a great workout for a number of reasons. First, it is low impact so it is easy on your joints. Second, it works multiple muscle groups at the same time including your legs, back, and arms. Third, it is an excellent cardio workout that will help you build endurance and stamina.
A 5k row is a good workout because it is challenging but doable for most people. It will get your heart rate up and help you burn calories. Rowing at a moderate pace for 30 minutes can burn around 300 calories.