Pretty.
Water cooling is not for me, but I admire the clean look of it in other people's systems.
Fun fact: I played with peltier coolers back in the AMD K6 / Pentium MMX days. One day I started getting frequent blue screens of death. Eventually I removed the peltier cooler from my CPU intending to re-seat it, and discovered my CPU had mold growing on it! The cooler was cooling too well. It was freezing the thermal paste, the CPU was melting the frost, and water was condensing onto the chip. True story.