I was looking through Selma's diary and found that she purchased her bathing suit for $4.98 on August 15, 1918 from Akron Dry Goods. I just discovered an interesting resource on Ancestry.com. They have scanned in what looks like every Sears Catalog from 1896 through 1993. In the picture I posted of Selma swimming earlier in the week, you couldn't really see what her bathing suit looked like. Here is the only page of bathing suits from the Spring 1918 catalog. I imagine that Selma's suit would have looked very much like these:
Here are pictures of more fashion-forward suits from 1918, not likely that the conservative Brueggeman's would have allowed (or could have afforded) these suits.