You need something to keep firm footing as others have mentioned. Several years ago while I was wet wading in Teva sandals my feet went out from under me. My leg slammed into a sharp ridge of shale. I let it bleed out for a while, gobbed it up with triple antibiotic and then used three butterfly closures to hold it shut. Fortunately it didn't get infected. I probably should have gone for stitches but I didn't want to hike out.
I'm a big fan of the Chota Hippies that LRO carries. They are super light, I believe I read 10 ounces each. You can wear them at 3 different heights depending on the temperature and use your wading boots for good footing. There are also the Simms neoprene socks that allow you to wear your regular wading boots and still have the wet wading feeling.