If neither work, you could even look into a fishing shoe like the Simms RiverTek BOA Boot ($170). It's a light hiker that is designed to be in and around water and slippery rocks. They're high tops, however, so even though the uppers are made of breathable synthetic, they're still apt to feel a bit warm. And they aren't really meant for hiking.
You could even try a slip-on like Muck's Cikana Shoe ($80). They're light and comfortable, and designed for wet and slippery conditions. They're made from a neoprene-like material, which isn't breathable, but they are low-cut. And you always can douse your feet in a stream!