I am 68 and am in a swimsuit everyday. I am a Red Cross certified lifeguard at our local rec center and I swim laps for fitness five mornings a week. I always wear a one piece. For lifeguarding and laps I wear Lands End suits usually with high necks and back hooks or back cross straps. At our lake house in the summer I like strapless suits. My favorite brand lately is Maxine of Hollywood. I usually wear a pair of pull on shorts over the suit if I want to feel a little more covered. I don't like tankinis. Unless you are standing still there always seems to be skin showing where it shouldn't.
Kudos to all who enjoy the beach and swimming no matter your size or shape. Love that attitude!