I bought this knee-length halter-top sundress at a thrift store for 10 cents. It would have made a lovely swimsuit coverup, but it was one size too small...so out came the scissors and pins.
This was a really simple retrofit for my 5-year-old. I took in the sides first. Then I marked new armholes (using the highly sophisticated "eyeballing it" method), keeping the original back and zipper. I removed the grosgrain ribbon binding from one of the neck ties and used it to bind the new armholes and neckline. Finally, I used the other tie to make the two shoulder straps.