It works the other way too. I didn't have access to a wind tunnel so I once did drag tests on a model car in a swimming pool. I used an electric motor and measured the current draw. It turns out you can get a close approximation to air at a much slower velocity because the Reynolds number must be the same - higher density medium so lower speeds. After calculating the drag coefficient I then compared it to one derived from full-scale coast down tests at freeway speeds. They were within about 20% of one another as well as the manufacturers published number. Certainly not accurate enough for commercial work but cheap, interesting, and I learned something which was the intended purpose anyway.