A Dry Ice effect is the projection of a dense cloud of smoke during a slow dance which settle's on the floor simulating a dancing on the clouds effect. The clouds of smoke generated by a dry ice machine are denser than air hence does not rise above the waist of the dancing couple thus creating a romantic and unforgettable scene that is ready to be captured by your camera-men.
Intelligent lights can be used to project a color wash on this dense cloud of smoke to change its color from white to any color if desired. Since this effect is specifically recommened for slow dances, it usually lasts for 3 - 4 Minutes afterwhich it dies out slowly as the music fades out.
The main difference between a Dry Ice effect and a Fog effect is that a Fog effect disperses all over the place, while a Dry Ice effect stays on the floor hence doesn't affect photography and videography.