Swimming can help you develop a six-pack, but it's not the only factor. Different swimming strokes target different muscle groups. Breaststrokes can strengthen your waistline and glutes, while front crawl and backstroke can work your obliques and melt away love handles. However, the butterfly stroke is considered the best for toning the abs. To gain muscle and effectively develop a six-pack, you should aim for at least two to three swimming sessions per week, with each session lasting about 30 to 60 minutes. Gradually build up your swimming routine, focusing on proper technique to prevent overexertion or injury. Keep in mind that combining swimming with a balanced diet and other exercises can optimize your results.