A device for introducing heat energy into a body of water and for extracting heat energy from the body of water, - the device comprising a hollow space so that said device floats when placed in the body of water, - the device comprising a water heat exchanger at least partially immersing in the body of water after the device is placed in the body of water, - the water heat exchanger comprising an intake for a heat transfer fluid and a discharge for the heat transfer fluid, so that the heat transfer fluid can flow through the water heat exchanger and in doing so give off heat energy to the body of water or extract heat energy from the body of water, characterized in that the device further comprises an air heat exchanger, - wherein the air heat exchanger comprises an air inlet for taking in ambient air and an air outlet for discharging the ambient air previously having entered the air heat exchanger through the air inlet, - wherein the device comprises at least one fan by means of which ambient air can be displaced through the air inlet into the air heat exchanger and then through the air heat exchanger, - wherein the air heat exchanger further comprises an inlet for the water originating from the body of water and an outlet for the water fed in through the inlet, so that water from the body of water can flow through the air heat exchanger and then exit the same, and - wherein the air heat exchanger comprises at least one partition by means of which the water flowing through the air heat exchanger is separated from the ambient air flowing through the air heat exchanger and through which heat energy can be transferred between the ambient air flowing through the air heat exchanger and the water flowing through the air heat exchanger. - the device comprising a hollow space so that said device floats when placed in the body of water, - the device comprising a water heat exchanger at least partially immersing in the body of water after the device is placed in the body of water, - the water heat exchanger comprising an intake for a heat transfer fluid and a discharge for the heat transfer fluid, so that the heat transfer fluid can flow through the water heat exchanger and in doing so give off heat energy to the body of water or extract heat energy from the body of water, - wherein the air heat exchanger comprises an air inlet for taking in ambient air and an air outlet for discharging the ambient air previously having entered the air heat exchanger through the air inlet, - wherein the device comprises at least one fan by means of which ambient air can be displaced through the air inlet into the air heat exchanger and then through the air heat exchanger, - wherein the air heat exchanger further comprises an inlet for the water originating from the body of water and an outlet for the water fed in through the inlet, so that water from the body of water can flow through the air heat exchanger and then exit the same, and - wherein the air heat exchanger comprises at least one partition by means of which the water flowing through the air heat exchanger is separated from the ambient air flowing through the air heat exchanger and through which heat energy can be transferred between the ambient air flowing through the air heat exchanger and the water flowing through the air heat exchanger.