From what I can see Blowfish sandals sold at Office seem to be synthetic. But the sole of the Dune one is also synthetic so probably equally sweaty. I like a completely flat leather sandal though. Dune one looks nice though, I like the single wide strap over the toes. I'll reserve judgement on the Blowfish ones because some that Office sell are gorgeous and some are not. None are fuddy duddy though!