Here are a few things to keep in mind when you go:
Have some sort of water shoes that stay on your feet. Chacos, Tevas, or Keens are a good idea. Flip flops are risky, as they can slip off easily. Either way, you’ll need something on your feet when you hop out of the water and have to trek across a hot, rocky surface to your car or shuttle.
Buy a waterproof pouch to wear around your neck for any essentials like car keys or phone. Consider having your sunglasses on a strap as well, in case you fall in.
Have fun! This is pretty much a given, though.
For more information on floating the river, including safety tips and a handy map, check out this page from Bend Metro Parks & Rec.