Posted August 6, 2007 8:22 a.m. EDT
Here's a fun video with some scientific underpinnings. These guys have filled a tub with a gas called sulfur hexaflouride. It's six times heavier than air. Watch the video as they put a little foil boat in the tank!
Another video on YouTube shows a guy inhaling it. Because sulfur hexaflouride is more dense, it has the opposite effect of helium on the voice!