Using water and other liquids like nitrogen to cool an overclocked computer or gaming rig is nothing new.
To be sure, we've seen plenty of liquid-cooled desktops and even some liquid-cooled laptops over the years. Typically, someone will choose a liquid cooling option simply because traditional air-cooling isn't enough to keep high-powered CPUs, GPUs, and other components cool when they're subjected to extreme loads.
Often one of the benefits of lower power computing devices such as the Raspberry Pi is that they produce very little heat, so you typically don't need a fan at all, as the processors can be passively cooled. Of course, that doesn't mean you won't find geeky hardware modders who want to use liquid cooling for devices like the Pi.
This is probably exactly what a hardware tweaker named Phame decided to do when he designed The Wet Pi. The Raspberry Pi has minimal specs with the 700 MHz processor, but you can overclock that processor to a cool 1 GHz. Phame created his own custom case complete with pink colored water that is circulated through the three hottest components on the little developer board.
The Pi's USB port provides the power needed to circulate the cooling water through the board. This is certainly very interesting project, even if it's somewhat unnecessary.