If it's just two people going, without a cooler, any suggestions for bringing a couple bottles of water along?

If you don't have a cooler. Get a backpack put a big trash bag in it fill it with ice. And all your drinks. That works great as a cooler on the river.

They have a snack bar at the buses, also you can rent a tube with a cooler attached

Tru

Absolutely..it usually takes about 3 hours and its hot..

They also have floating barrels you can rent just bring bags of ice

Highly UNRECCOMEND. Bring a small cooler with at least 6 bottles of water

A cooler would be best, second best is to rent a tub from the tubing place (if you are using salt river tubing company). If not then just bring a plastic bag.

A backpack :)

Yes I would bring water along. It's freaking hot out there even though the water is cool.

Largest ones, best if frozen