Lindsay from Diary of a Crafty Lady made this Towel Vest swim cover-ups from a towel. It slip on like a jacket, with ties at the front to keep it put. The design is based on a cover-up that her grandmother made for her when she was a child. It was so convenient that she decided to make more for her girls. You can adjust the size by using a different sized towel. Go to her blog for a tutorial.
[photo from Diary of a Crafty Lady]
By Anne Weaver