I swim as a workout! I do 3km a week of laps. I'm two months out and lose an average of 3lb a week (with a surgery day BMI of 36). Swimming is great for me because it's very calming, it doesn't cause my body pain and I could do it at any weight, I don't feel like a sweaty overheated mess, and I'm able to measure my successes/growth. the best workout post surgery is the one you can enjoy and stick with. ANY form of exercise is going to be incredibly beneficial to your progress, overall health and quality of life, and your ability to maintain weight loss.