A nozzle for a liquid-cooled plasma arc torch, the nozzle comprising: a thermally conductive body having a distal end, a proximal end, and a longitudinal axis extending therethrough; a plasma arc exit orifice at the distal end of the thermally conductive body; a cooling waist located circumferentially about an exterior surface of the thermally conductive body, the cooling waist including: a liquid inlet slope disposed about a circumference of the thermally conductive body for receiving a liquid coolant flow toward the nozzle, a liquid outlet slope disposed about a circumference of the thermally conductive body and located at a different axial location along the longitudinal axis from the liquid inlet slope, and a heat exchange region between the liquid inlet slope and the liquid outlet slope, wherein the heat exchange region extends substantially parallel to the longitudinal axis and wherein each of the liquid inlet slope and the liquid outlet slope is oriented at a non-zero angle to the longitudinal axis; the nozzle further comprising: a first sealing member located between the liquid outlet slope and the distal end of the thermally conductive body; and a second sealing member located between the proximal end of the thermally conductive body and the liquid inlet slope, characterised in that the cooling waist is configured to facilitate a laminar flow of a liquid coolant through a chamber defined in part by the cooling waist such that the liquid coolant entering the liquid inlet slope does not substantially intermingle with the liquid coolant exiting from the liquid outlet slope. a thermally conductive body having a distal end, a proximal end, and a longitudinal axis extending therethrough; a plasma arc exit orifice at the distal end of the thermally conductive body; a cooling waist located circumferentially about an exterior surface of the thermally conductive body, the cooling waist including: a liquid inlet slope disposed about a circumference of the thermally conductive body for receiving a liquid coolant flow toward the nozzle, a liquid outlet slope disposed about a circumference of the thermally conductive body and located at a different axial location along the longitudinal axis from the liquid inlet slope, and a heat exchange region between the liquid inlet slope and the liquid outlet slope, wherein the heat exchange region extends substantially parallel to the longitudinal axis and wherein each of the liquid inlet slope and the liquid outlet slope is oriented at a non-zero angle to the longitudinal axis; the nozzle further comprising: a first sealing member located between the liquid outlet slope and the distal end of the thermally conductive body; and a second sealing member located between the proximal end of the thermally conductive body and the liquid inlet slope, characterised in that the cooling waist is configured to facilitate a laminar flow of a liquid coolant through a chamber defined in part by the cooling waist such that the liquid coolant entering the liquid inlet slope does not substantially intermingle with the liquid coolant exiting from the liquid outlet slope. a liquid inlet slope disposed about a circumference of the thermally conductive body for receiving a liquid coolant flow toward the nozzle, a liquid outlet slope disposed about a circumference of the thermally conductive body and located at a different axial location along the longitudinal axis from the liquid inlet slope, and a heat exchange region between the liquid inlet slope and the liquid outlet slope, wherein the heat exchange region extends substantially parallel to the longitudinal axis and wherein each of the liquid inlet slope and the liquid outlet slope is oriented at a non-zero angle to the longitudinal axis; the nozzle further comprising: a first sealing member located between the liquid outlet slope and the distal end of the thermally conductive body; and a second sealing member located between the proximal end of the thermally conductive body and the liquid inlet slope, characterised in that the cooling waist is configured to facilitate a laminar flow of a liquid coolant through a chamber defined in part by the cooling waist such that the liquid coolant entering the liquid inlet slope does not substantially intermingle with the liquid coolant exiting from the liquid outlet slope. a first sealing member located between the liquid outlet slope and the distal end of the thermally conductive body; and a second sealing member located between the proximal end of the thermally conductive body and the liquid inlet slope, characterised in that the cooling waist is configured to facilitate a laminar flow of a liquid coolant through a chamber defined in part by the cooling waist such that the liquid coolant entering the liquid inlet slope does not substantially intermingle with the liquid coolant exiting from the liquid outlet slope.