Abstract: A liquid coolant heatsink apparatus is provided for cooling devices, such as heat dissipating electronic components. The heat sink apparatus comprises a cooling plate having an outer side for mounting of the device and an inner side formed with a plurality of recesses. A sealing assembly, comprising a base plate and a number of baffles is disposed opposite the inner side of the cooling plate to define a space for circulation of the liquid coolant. The baffles include a plurality of projections which correspond to the recesses and project into them to encourage turbulent flow of the liquid against the inner side of the cooling plate. The baffles are retained in position between the cooling plate and the base plate.