swim suite? is it possible?

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i am supposed to be studing for exams, so of course the only ting going through my mind are millions of craft ideas, not millions of math problmes. anyways, does anyone know anythign about making a swim suite out of a material that is:
55% polyester
35% cotton
10% spandex ?
i know how i would cut it to make the pattern, but i'm just wondering about stretching in water, advice on elastic or anythign else so that it doesn't fall off!
any comments would be helpful!