Pleeeeease buy good expensive shoes if you decide to take up walking. You just cannot walk successfully in old shoes or shoes not meant for walking. I recommend New Balance. I walk about 10 miles a week and my feet, legs, knees, hips and back don’t hurt a whip even though I carry around an extra 150 lbs.
You also want good shoes for land aerobics.
I also swim once a week and I love it. I go for an hour straight. No routine, just keeping the heart rate up. I couldn’t do it without my iPod case and headphones from H2Oaudio.