On warmer dryer days I wear Karrimor Low Mount shoes. They are not light for shoes, but they are really comfy and cooler than boots in the summer. I have an old pair that I sometimes carry, if I'm planning to ford a river that is going to come above my gaiters. I've tried wearing them in cool wet conditions, but they don't work for me. Much prefer the security of a good solid boot protecting my feet and ankles in such conditions. Dry feet is a bonus prize.
I've mentioned before about body boarding surf socks. Comfy and very waterproof. But also thick, so a tricky one with shoes.