sirleechalot wanted to build himself a new PC, one with a BioShock twist, so he did just that. The twist being almost the entire thing is submerged in liquid.
While it looks like water, it's in fact mineral oil, which many endorse for its cooling benefits, but which sirleechalot just wanted to use because it "looked really nice". No arguments here.
Only the HDD is left out of the oil, the rest dunked under the surface and guarded by a Big Daddy.