The practicality depends somewhat on the water depth you expect to ford.
I was headed to Alaska's Denali National Park, and the park rangers warn visitors that the streams are all over the place, and the water is very cold. So, I constructed some "waders" made out of heavy transparent polyethylene bags. The bags were very long and narrow, so I could slip my feet in. To prevent a stream bed rock from puncturing them, I made soles out of Reflectix, and fixed them on the bottom, both outside the plastic and also inside. To hold the tops on my thighs, I used rubber bands. The pair weighed two or three ounces.