1. An apparatus for cooling one or more heat generating components, the apparatus comprising:an enclosure defining a volume containing: a first liquid coolant, and the one or more heat generating components immersed in the first liquid coolant;
a heat exchanger unit comprising a conduit surrounded by the volume, the conduit enabling a second liquid coolant to enter and leave the enclosure, the conduit providing a fluid-tight seal between the first liquid coolant and the second liquid coolant when the first liquid coolant within the volume surrounds the conduit; and
a pump within the enclosure configured to direct the first liquid coolant horizontally:over a plurality of hot areas that form from the one or more heat generating components, such that heat is exchanged from the one or more heat generating components to the first liquid coolant, and
via a pipe or duct disposed entirely within the enclosure to or from the heat exchanger unit such that the heat is exchanged between the first liquid coolant and the second liquid coolant.