The false statement about countercurrent heat exchange is: "Countercurrent heat exchange reduces moisture levels inside the lung cavity." This statement is false because countercurrent heat exchange primarily facilitates heat transfer between fluids flowing in opposite directions, not moisture control inside the lung cavity. Moisture levels in the lung cavity are regulated by respiratory processes rather than countercurrent heat exchange. Other statements about countercurrent heat exchange—such as it keeping heat out, providing heat to cold blood, cooling hot blood, and increasing muscle power—are true, as this mechanism helps maintain temperature gradients, conserve heat, and optimize physiological functions.