An apparatus for cooling one or more heat generating components comprises: a sealable enclosure defining a volume for containing a first coolant and one or more heat generating components; a conduit surrounded by the volume, the conduit enabling a second coolant to enter and leave the enclosure, the conduit providing a fluid-tight seal between the first coolant and the second coolant when the first coolant within the volume surrounds the conduit; and a pump within the enclosure configured to direct the first coolant to the conduit such that heat is exchanged between the first coolant and the second coolant.