An apparatus for holding and cooling rack-mountable servers having heat-producing electronic components includes a tank, a volume of dielectric liquid coolant in the tank, mounting members that hold rack-mountable servers in the tank, one or more pumps, fluid velocity augmentations devices, and a liquid-to-liquid or liquid-to-refrigerant heat exchanger outside of the tank. The mounting members hold the rack-mountable servers in a vertical orientation within the tank such that the servers are commonly submersed in the volume of the dielectric liquid coolant. When a pump is operated to move the dielectric liquid coolant vertically across the heat producing components of the rack-mountable servers, a circuit is formed in which a first portion of heated dielectric liquid coolant is moved vertically upward across the heat producing components and then downward outside of the rack mountable servers in a passage external to the rack-mountable servers, while a second portion of heated dielectric liquid coolant flows out of the tank and through the liquid-to-liquid or liquid-to-refrigerant heat exchanger.