(Really long) Picture Tutorial
cut strip of red for ruffle.
Make a sandwich with ruffle and straps inside the two layers of front side of top.
Sandwich the other end of the straps in the back of the top.
Sew all the way around and turn right side out. (Make sure your straps are close enough together to stay on the shoulder, unlike mine.)
Cut front of shirt bottom and ruffle the bottom. (I did this with a zig zag stitch and stretched the fabric as I sewed.)
Cut back of shirt bottom and ruffle the same way.
Sew all together. Pin to swimsuit top right sides together with overlap in the back.
For the bottoms I made my pattern from a pair of leggings and added a strip of red to the top.
(More pictures of completed swimming suit to come later)