One of my all time favorite video games on the PC was Bioshock. The game had a great storyline and fantastic graphics in a creepy environment that made me jump more than once. A dude has taken the Bioshock theme and used it to create his own casemod.
The guy submerged all the components of his PC except for the storage drive in a small plastic aquarium filled with mineral oil. The guy mounted the mainboard, which runs an Intel Atom processor, and the power supply to an acrylic sheet that sits at the back of the case. The mineral oil was purchased online and it took four gallons. Disgustingly the stuff is actually sold as a horse laxative.
The guy picked up a Big Daddy figure on Amazon and crammed it inside the case to protect his hardware. The other components of the system are straight out of the fish department at your local pet store with black gravel, a bubble filter, and a few other things. Check out the video below.