Caroline Kennedy may be in her mid-50s, but you'd never know it by looking at her ageless figure!

The best-selling author, who keeps a rather low profile despite her fame (she is the late John F. Kennedy's only surviving child), made a splash in St Barts on Saturday, where she hit the beach clad in a purple bikini.

Showing off her rock-hard abs, sculpted arms and shoulders and slim legs, the high-profile redhead appeared to be enjoying her fun in the sun with her husband Edwin Schlosseberg, who she's been married to for 26 years.