My friends and I were just discussing how we all feel like the best shape we've ever been in was when we were swimming a lot. This led me on a hunt for cute swim caps (since none of us are racing anymore, a little style can't hurt).
Turns out other people have swim caps on their minds as well. Joy turned me on to these amazing pictures by Koto Bolofo. I haven't found those exact caps yet, but here's some really good (and cheap!) alternatives. Not all are vintage (chlorine will kill your cap eventually), but they've definitely got a nice vintage vibe:
The minimalist. (scroll down a bit to the bubble head crepe cap). It's the chin strap what does it for me.
I love the sculpted flowers on the "Latex Flower Swim Cap" (from the same site as the bubble head crepe cap)
This site has some good floral options, but their pictures are all copyrighted
As always, an ebay search turns up great stuff. In this case, most of the "vintage ones" are actually just the ones I've listed above. This one is dreamy though.