Four Person Costume Ideas "Four Seasons" Costumes?

"Four Seasons" Costumes? - four person costume ideas

My three friends and I (all girls to go 13-14 years old) to the theme of our clothing, how) the fairies of the four seasons (spring, summer, autumn, winter. We are with Halloween costumes for my dance school. Summer, I do not know what should I wear or where you got it.
I checked some local thrift stores and find nothing, or take had nothing to do with summer dress or at least have. Difficult!
I like the idea of a swimsuit and flow around my waist, there is no ego at all, and it is very revealing. I want the season, not one person in the season. I also want something nice, do not wear stupid. Ideas? (And note that I live in Canada, not always 21 or Macy's or something.)

Thank you very much!