The very deepest water is isolated from the rest of the Canada Basin and has likely been there for about 500 yrs. Hence, it is possible to detect the effects of geothermal heating from the sea floor. The bottom layer of water, which has a thickness of up to 1,000 m, is completely mixed, likely by convection from this heating. Small changes in temperature of this well-mixed layer will tell us, for example, how long this heating has been taking place (i.e., how long the water has been there), and whether the geothermal heat is remaining in the deep layer or escaping through the top. Our preliminary temperature measurements over the past decade indicate that most of the heat input is indeed escaping.