I documented my experiment on the youtube video below. I didn't try different water temperatures, but from my experience room temperature (~76 degrees Fahrenheit) water always works best.
Here is my youtube video with the results of my experiment: 
Water marbling is tons of fun and you get a unique look to your nails.  If you want a step by step how to please watch this video: http://www.youtube.com/watch?v=-YoxnPMbVhA  There are detailed instructions there.  
For those of you who are too lazy to watch the which type of water experiment here are the results:
the type of water does not seem to make a difference.  So have fun water marbling, and don't waste good bottled water!

 








