03/2011 issue of Ottobre. I have used this issue a ton! It has a lot of really great, versatile styles in it. This suit is #30, the Mermaid swimsuit.
This is a quickie, but hopefully useful. This pattern didn't include specific lengths for the elastic in the leg, arm and neck openings. Fortunately, the Singer Sewing Activewear book has a handy chart so that you can figure it out yourself. This is especially great if you need to alter an opening for fit or personal preference. Since the book is out of print, I'm going to share the chart here.