I will take this time to bring to light the general suckiness of the safety regulation or whatever it is that encourages female astronauts, especially the ones with really long hair, to keep it tied back. Honestly, even these shots were hard to find.
Well, water has a tendency to change the texture and suppleness of the hair as well as subjecting it to more disruptive turbulence. In addition, gravity is still not absent, so the hair is then subjected to the downward force, and if it is still bouyant, the effects of the bouyant force. If the astronaut in the first two shots there was submerged in water in gravity, her hair wouldn't be as neat and regular as that, it'd be much more wild and sticking to itself and so forth. I think you'd also see more of a sense of the hair folding around itself in layers that are parallel to the ground. If she was plunging down, that would also be inacurrate as the lack of gravity means that no noticeable force is acting on the hair. Plunging down in water would pull the hair up farther than it would be in zero gravity.
As for roller coasters, that's more likely, but it would need to be one of those "free-fall" coasters that are nothing but a straight drop.
It's pictures from NASAs college student program. They allow college kids to ride on their zero g simulation plane, which flies in a parabolic arc and simulates zero g for periods of about 25 seconds at a time.
There are thousands of photos to sort through, and I wanted to provide direct links to all the best pictures, but they don't allow direct linking for some reason. But you can find lots of pics with long floating hair.
I threw together a yahoo web site with a few of the good ones as samples.