In a swimming workout, water is the natural resistance that works against the body while supporting it from all sides. It helps to strengthen muscles and challenge the heart to work harder, improving cardiovascular fitness while burning calories.
Whether you go swimming every day or three times a week, any amount of time in the pool is good. Having a dedicated workout can help you see progress by pointing you in the right direction, so you know what you're doing when you get in the water, and it can help increase your motivation.