Swimming

Hello everyone.  I am new to this forum.  I am a 25yr old female that had the gastic sleeve excactly a month and day ago.  I attempted to hit the treadmill yesterday for 1/2 hour but I only walked at a very slow 2.6 pace and I didn't feel tooo well.  I then opted to go to the pool and do some laps.  It was GREAT!!!   How is swimming as an excerise?  I would love to hear your opinions Thanks!!

Ive always heard that swimming and aqua aerobics are great forms of exercise, and they're low impact.  I hurt my knee doing step aerobics and switched to swimming.  I swam 10 laps the first time, hadn't swam in like at least 5 years.