My girlfriend and I are visiting Zion National Park over Labor Day weekend and we are planning to do the bottom up hike (go up a few miles and then turn back) rather than the more strenuous top down 16 miler. We're both in very good shape but have never tried a river hike like this before so we don't want to bite off more than we can chew 
I've googled and seen some recommendations for the Canyoneer 5.10 shoes for this hike, but those seem like they might be kinda overkill what we are doing. The water won't be freezing this time of year, and we'll only be in the water 4-6 hours, and I'm thinking this recommendation is for people doing the full hike and perhaps during cooler months. Mainly though she's not at all keen about the idea of RENTING shoes, and they are way too pricey to buy them when we have no idea when we would ever wear them again.
Obviously open toed sandals are a bad idea with submerged rocks and sticks, but wouldn't an old pair of tennis shoes with wool socks work? (with maybe an extra pair or two of socks brought along just in case) Or even some ordinary water shoes, so long as they have a fairly sturdy bottom and heel & toe protection?
If we end up with feet a bit sore or have a blister or two no big deal, but if people think we're really at risk for something worse than that by not going with the Canyoneers or equivalent I may have to encourage her to overcome her phobia of wearing shoes 50 other people have worn before
Thanks for any help or recommendations anyone can offer!

I've googled and seen some recommendations for the Canyoneer 5.10 shoes for this hike, but those seem like they might be kinda overkill what we are doing. The water won't be freezing this time of year, and we'll only be in the water 4-6 hours, and I'm thinking this recommendation is for people doing the full hike and perhaps during cooler months. Mainly though she's not at all keen about the idea of RENTING shoes, and they are way too pricey to buy them when we have no idea when we would ever wear them again.
Obviously open toed sandals are a bad idea with submerged rocks and sticks, but wouldn't an old pair of tennis shoes with wool socks work? (with maybe an extra pair or two of socks brought along just in case) Or even some ordinary water shoes, so long as they have a fairly sturdy bottom and heel & toe protection?
If we end up with feet a bit sore or have a blister or two no big deal, but if people think we're really at risk for something worse than that by not going with the Canyoneers or equivalent I may have to encourage her to overcome her phobia of wearing shoes 50 other people have worn before

Thanks for any help or recommendations anyone can offer!