Over the years, I have laid eyes on some strange casemods and have seen more than one machine that was submerged in oil. A new casemod has surfaced that has a Bioshock theme. The builder uses an aquarium to put his new HTPC under four gallons of mineral oil.
The mineral oil is normally used as a laxative for horses apparently. The mainboard and PSU are mounted to a clear plastic sheet and placed into the aquarium. The only hardware part not under the oil is the HDD. The maker rounded the design out with a bubble filter, gravel and a few other things.