Was it this Leap-controlled fluid simulator – also seen on this massive touch screen?
Very early (before we created our launch video in May 2012) I put together a fluid simulation demo using MT4J, a multitouch framework for Java, based on their fluid simulation example. It didn't even use the Leap API (we didn't have an API at the time) – it simply sent touch events to Windows using a multitouch driver we built that ended up in Touchless for Windows. You can probably compile what they have (beware the 64-bit Java compiler, there are 32-bit DLLs!) and use Touchless for the same effect, but it's 2D so Leap doesn't have much advantage over multitouch for that demo.
If you want 3D fluid simulation that's far superior, launch Orientation from Airspace Home. The fluid dynamics simulation code is based on a variant of MSAFluid (in 2D) that our summer-2012 intern Alex extruded to work in 3D.
Alex has built lots of cool stuff, like the physics groundwork for Block54 and this awesome 2D Portal game on TI-83/84 calculators, which he wrote with the Axe parser that our tracking engineer Kevin created. Small world!
Alan