Like that. In the world of multitasking and multi-purposeful, we tend to lose sight of the aesthetics (pun intended). Douglas Hamilton came up with this design where your flip flop can be worn as a thong.
Each thong has a super elastic strap that you can pull to stretch out and just stand right in it to be a thong. I'm pretty sure it wouldn't be comfortable. Then again, I could just picture a brand name or logo plastered at the bottom of the flip flop being 'advertised' when converted to a thong.
I do think covered shoes would make a better, uhm, fit.
More info here.
