Recently I had a shoot that called for a dreamy, cloudy effect. I decided to use dry ice rather then a smoke machine because dry ice smoke stays lower to the ground, which would highlight the products better. It sure makes a project interesting when you have an uncontrollable, organic element in the photo. At several points most of the floor in my entire studio (not just the set!) was covered with the fogvery surreal.
On the technical side, the dry ice effect doesn't last very long and we had to come up with ways to prolong it. The dry ice becomes especially activated when placed in hot water. At first we used the hot water from the tap and it didn't fog up very high. We found that boiling hot water really made the fog go into overdrive. We rented 3 large coffee carafes and used them to make gallons of boiling hot water. Next time I might even use a 4th carafe. They are power hogs and kept blowing a fuse, so we had to put each one on it's own breaker.
Most of the time we placed the blocks of dry ice in bowls on the floor, which created a really nice, billowing, San Francisco fog look. I found that to give the fog some more shape it helped to pour it out of buckets. The fog looked great but it disappeared fast.
Overall, the dry ice and it's fog doesn't get things wet (hence the name dry ice). But because of the method of keeping it in hot water, sometimes when we poured the smoke from the buckets we also poured a little water on the floor. Luckily the fog covered the floor and the puddles were not visible.