If you're looking for a low-impact activity that engages multiple muscle groups, improves cardiovascular health, and promotes mental health, swimming may be a better choice for you. If you're looking to lose fat, build muscle mass, and increase strength and power, gym workouts may be a better choice.

The "better" choice depends entirely on your specific fitness goals and physical health. Swimming is a superior "full-body" cardiovascular workout that is low-impact, making it the best option for those with joint pain, injuries, or obesity. It improves lung capacity and tones muscle through water resistance without the risk of heavy impact strain. On the other hand, the gym is significantly better for hypertrophy (muscle growth) and bone density. Resistance training with weights allows for "progressive overload," which is the most efficient way to build raw strength and a sculpted physique. Many fitness experts suggest that a combination of both is ideal: using the gym for strength and bone health, and swimming for active recovery and cardiovascular endurance. If weight loss is the primary goal, swimming can burn 400–700 calories per hour, which is highly competitive with traditional gym cardio like the elliptical or treadmill.