I remembered seeing a photo like this a few years ago and thought I'd give it a try as I recently picked up a small tank that I use for various photography 'experiments'
It is a simple set up, lighting as shown in my previous blog post.
I ran a tube along the bottom of the glass fish tank and filled it to the top with water. I hung a martini glass from a stick into the water above the tube. Blowing bubbles into the glass via the tube until there was enough air to 'tip' the glass up and release the air... I shot the picture as the air bubbled.
The photo has been rotated in photoshop CS5 to give an illusion of liquid being spilled